A few questions in Preparation for the trip

We're staying in that same hotel in Barranco. Supposedly that neighborhood has a lot of nightclubs and romantic places to eat dinner, but not a lot of museums and sights.

Barrancas may be a different town on the Northern coast, north of Lima, if I remember my guidebook correctly. Not trying to nitpick, but it's better to use the proper name of the town for when people do searches & such.

There are ATMs in Cuzco, but as far as I have been able to find out not in the SV and definitely not at Aguas Calientes.

1. It is not necessary to have a guide for the sites in the Sacred Valley, but what people normally do is take a tour from Cuzco that takes in all of the sites in one day (with the exception of Maras Moray which can be done on a really cool mountain biking tour, arranged from Cuzco. A reputable agency is "Loreto Tours"). Take your pick with the reading guides, lonely planet, rough guide or any of the others are all pretty ordinary. Guides will find you if you go to each site on your own.
   
   2. The airport in Lima does a rubbish exchange rate. It is difficult (but by no means impossible) to change money in the Sacred Valley, and you would get a better rate than at Lima airport. Your best bet is around Barranco, ask at the hotel where the best place to change money would be. You must also be going to Cuzco, there are loads of places to chage money there on the Av. del Sol.
   
   3. There are ATMs at Lima airport (try to avoid the "Global Net" ones, as they charge a lot for withdrawals (they are also the easiest to spot). There are also loads in Cuzco (you must be going there as well, right??). There are ATMs in the following places (not Global Net): Pisac, Urubamba, Ollantaytambo and Aguas Calientes, but you have to ask around to find them. The one at Urubamba is the easiest to spot and belongs to the BCP. The one at Ollantaytambo is inside the reception of a hotel near the main plaza (ask around) and in Aguas Calientes there is one on the railway tracks (but sometimes it runs out of money.
   
   4. In Barranco, go to the "Puente de los suspiros" and have a smooch, then walk down to the lookout point over the beachs (don`t go if there are only a few people around, as the area is a little bit dodgy). If you are there on a Sunday, enjoy the Traditional Food Fair on the plaza and then go for some cocktails (there is a cool place in an old railway carriage on the plaza, and a nice café called Sancho Panza just 1/2 a block away from the plaza. If you like electricity, there is the electricity museum!!! I guess that should fill your free time there!
   
   Enjoy!!!

Before leaving, if possible, buy a copy of "Exploring Cusco" by Peter Frost. Or buy it at the South American Explorers Club in Cusco. Tons of information on the Sacred Valley, sites around Cusco, Machu Picchu, etc. Much more reliable than the hallucinations to be offered by your guide at MP...

Hi there,
totally agree with mikebrady regarding 1.
On 2., for sure at Second Home Peru. They can advice for the most convenient place to exchange your money, be it a bank or an exchange agency. By the way, nice hotel choice. The house is historic and the view of the Pacific most beautiful.
3. You find plenty ATMs in Cusco, and also in Urubamba.
4. Here you find a list of bars and shops in Barranco. Dédalo is probably a must if you are interested in arts and handicrafts. Opposite the square from Dédalo, you find one of Lima's most renowned art galleries (De La Puente). Nearby you also find the Puente de los Suspiros, a nice angle of Lima, old style.