7-10 days in Cambodia

1. yes
2. mix early morning and late evening and try and avoid worst of mid day heat
   2a. not a problem if you ride carefully but try and at least make sure you have a light on the back of the bike. The road back can be very busy
   3 yes and yes
   3a stay on marked paths
   4No
3. check out a guide book or travelfish
   6 up to you but I drink the water provided in restaurants and indeed elsewhere without any problem - if the locals drink it that is). Street food is usually safe but again this is up to you and might depend on your own constitution

I hired a bike last week through my guesthouse for €4 (U.S.) a day - didn't shop around so it's probably not the cheapest.
Lock it when you park it.
No lights supplied with any hire bike I saw in Cambodia - it might be an idea to bring a tiny LED one or a hi-vis belt/jacket with you.
Cycling around Angkor was pleasant in Feb as the trees give a lot of shade - no idea about July.
Street food is safe assuming you choose those that have local customers.

its not a problem at all to rent a bicyle in siem reap and its a great way to discover the amazing temples there. it does get very hot during the day, so getting a early morning start is a good idea. the best (and most visited) place for sunrise is angkor wat. make sure that you get there early enough (like 30 minutes before sunrise), so that you have time to choose your spot (with the many other visitors) and then enjoy the sunrise. after that, visit angkor wat, and have breakfast in one of the stalls next to temple (and maybe have look at the buddihst temple next to angkor wat as well).

i'm very much a temple "freak", i have been to siem reap 3 times, each for 4 days and will be back. besides the temples in the central area (around angkor wat), there are several amazing temples further out, which cant be reached by bicycle, so you might consider a day with a car or motorbike. banteay srei is beautiful, and very much visited. beng mealea is pretty wild and unvisited (compared to other places) and a real highlight in my opinion. i also like the rolous group, as few visitors go there, and there is a lively wat next door.

yes, you want to drink bottled water. i love street food, and of course you can get unlucky, but if the food is fresh (meaning - loads of locals are eating there), you should be fine.

in phnom penh, the 2 main sights are s-21 and the killing fields. both horrible but must see places. other than that, this depends on you. i like markets, so i would visit the central market and the russian market. for atmosphere, walk along the mekong (especially in the morning). visit the national museum and the palace.

Temples: Canby publications has lots of good information on Angkor Wat including suggested itineraries: http://www.canbypublications.com/angkor-cambodia/angkor-itinerary.htm

Bicycles: a lot of people don't realize how far it is between temples or appreciate how hot it can be riding between them. Be prepared and take lots of water. I see a lot of tourists riding back in the evening with no lights on their bikes. Personally I think they're crazy and they wouldn't do that at home.

Water: I've been told that the tap water in Siem Reap and Phnom Penh is actually of a high standard and drinkable. Not many people realize that. Nevertheless I don't drink it and prefer to use bottled water which is what pretty much everyone does.

Crowds: With over 2 million tourists annually it's hard to avoid the crowds in Siem Reap but the worst is Pub Street which is where all the backpacker and party crowd tend to congregate. If you don't like that atmosphere then choose accommodation away from there. Lots of good choices available. Same applies to restaurants.

July is rainy season so be prepared for it, especially if on a bicycle.

Re food: the freshness is not the main issue - most cases of "travelers diarrhea" are caused by fecal-oral transmission. Isn't that a charming thought.

Yes, bottled water all the way. In the old days (before bottled water), diarrhea was pretty much part of travel in SEA. Not so anymore. Good to drink lots of water while cycling around Angkor. Uomo's assertion that tap-water in PP is clean is accurate, but still...

I have never been to SE Asia in the wet season. Is the rain constant in July or are there just occasional afternoon electrical storms like you get in Sydney in summer? Is it a deluge or just light rain?

I may even consider going at an alternative time in the dry season if it is too unpleasant.

The rain in Cambodia absolutely buckets down when it rains. It's nothing like Melbourne /Sydney standard rainy days. My first time in Cambodia, much of the old market area in Sieam Reap was underwater (up to my thighs).
Personally, I think that it would certainly detract from any enjoyment going during the monsoon.

Better to wait for the end of the monsoon to travel. You'd enjoy it so much more.

1. Are there plenty of hire bicycles available in Siem Riep and what is the cost? Are all hire bikes of OK quality or should some operators be avoided?

There are hundreds of places that have bikes for hire. Costs vary but not by much. The average I've seen was US$2 per day.

1. Any ideas for the strategy eg. Early morning starts, what to see first in Angkor Wat?

Definitley early morning start but make sure you have a ticket (get it late in the day, the day before you intend going, to ensure it's valid when you are inside the park). If you have no valid ticket, you could be asked to ride back to the ticket booth and get a ticket before coming back.

2a. I presume that it is unsafe to ride at night but would like to get some sunset photos so perhaps some slow careful riding back to base?
3. Can bicycles be taken anywhere and if not should they be locked ?

Correct. I would buy a couple of good lights (rear reflector & very strong front light) to use when you are there. Also, there are very few people who use bike helmets. Take a good bike helmet with you. Personally, I'd rather look out of place and be safe in the case of a fall off the bike, by wearing a helmet.

Bikes cannot be taken into the temple complexes and should be locked outside. There's going to be places you'll be able to secure the bike but I would also take a good (lightweight) lock /chain.

Also, do some reading on the distances between the temples. They are not 5-10 minutes ride apart. It's a long journey for some.

3a. Are the landmined areas well signposted or are there specific no-go zones that i neeed to know?

Most of the tourist areas in Siem Reap (and especially around the temple complexes) have been cleared. There's nothing to worry about in the tourist areas. The only place I've read about recently, was in the Cambodia LP guide; there's a village East (?) of Battambang, which is still heavily mined and deserves caution when going off the track.

1. Any other recommendations with bicycle use?

Learn how to change a flat tyre; carry a small bike pump and other items that you deem necessary. I always prefer to ensure that contingencies are covered rather than be caught out in the middle of nowhere and needing to proceed a long way to get help.

1. My interests are history both ancient and modern eg Kymer Rouge, local culture, architecture and photography etc so what suggestions would you have for 3-4 days in Phnom Pehn?

As others have said; S21 (Toul Sleng) and the Killing Fields (there are many fields around Cambodia but the most widely known is the one outside of Phnom Penh). There's also the Royal Palace; Toul Tom Pong (a huge market full of almost everything you can think of)and the lakeside area (near the Royal Palace), for good eateries.

1. I presume that i should not drink the water other than from purchased sealed bottles but is street cooked food safe to eat or should I only eat at "clean-looking" (whatever than means) restaurants?

Restaurants are generally very good. You can find plenty of western style restaurants in most cities. There are many good Cambodian restaurants that have good food. Look for places where Cambodians are eating as an indication of whether the food is good (and /or cheap). Pub Street in Siem is good during the daytime but I find it's full of bogans during the nights. Restaurants /pubs all in a row and many with booming speakers trying to outdo each other to make their music heard (it just ends up being a din).

Water or, fresh coconut milk (available outside most temples) is widely available.

There are also many people selling paperback books about the temples (can't remember the name /author). Some people will ask US$30 for the book (the printed price on the back cover). You can get them for around US$7.50, because they are not original prints of the book.

My last suggestion is borrow the LP Cambodia guide from your library (some libraries have digital versions availalbe to borrow). I always recommend that people do some groundwork (read up before you go), on the country that is going to be visited.