Bang Saen is now just over an hour from Bkk - there is a motorway spur (Kho San Road) that goes straight into the town now. The old way in was from Sukhumvit down Rong Haad Road to the "beach roundabout" - a rather ugly monument at the beginning of the main part of beach road (Bang Saen Sai 1)
Bang Saen is extremely popular with bangkokians on holidays and W/Es and the beachfront can get rammed.
However in the week you will have the place to yourself.
in the last five years or so a lot of new hotels have opened up offering a wide price range.
Restaurants
Bang Saen has more seafood restaurants than you can throw a stick at....... in fact it's quite difficult NOT to eat seafood.....
Most will stay open in the week but some who cater for tour groups won't.
The main beach does not have particularly coarse sand but the system of renting tables and umbrellas means it isn't very cheap.
The South end (Wanapha Beach)is much less formal - many of the students from the nearby Uni have "picnics" there in the evening and there are plenty of food stalls and bigger sit down seafood restaurants.
For good food prepared in front of you - Andy's on beach road in front of the 7/11 is great. It appears on the sidewalk (nearly)every evening weather permitting and stays open to 10pm -ish....great seafood etc and won't break the bank. A lot of the staff speak English - they're students!
If you want a really good seafood restaurant - the best are between Bang Sean and Ang Sila (North coast of the town) head towards Ang Sila and turn down Rop Khao Sam Muk soi1 - the restaurant on the seafront there is fantastic - I'm afraid I can't remember the name -"เปี๊ยกมันทะเล" in Thai is one Google - Piekman Talay - I think. it's not cheap but does the most fantastic grilled prawns in tamarind sauce - and the mini-clams are out of this world.
Many people will recommend "Relax" - for me the live music is too intrusive and I find the food mediocre at best.
Pakarang is a large establishment at the Northern end of Bang Saen beach - very popular and I’ve found the food to be quite good. The car park is on the opposite side of the road on a band - it’s a wonder no-one is run over.
Minivans run into "Long Haad" - the road from sukhumvit to the beach.
However I would suggest not going by minivan but rent a car - Bang Saen is quite a "spread out" town and having you own transport is a boon.
I guess I could hire a motorcycle whilst there but they aren't very common. You can also rent tandem bicycles - but they can't be regarded as serious transport.
PS - If you want "authentic" Italian style pizza and other Italian food, San Marzarno (https://www.facebook.com/SanMarzano.Bangsaen/) on the Bang saen Ang Sila road is really rather good - with a European trained chef.