In reply to Braintax:
I went out to Huaraz on my own as part of my uni studies in 2003. At the time I had ice climbed about grade III and had done a handful of simple routes in Chamonix.
I ended up getting really quite a lot done and actually successfully pushing my alpine grade. It was an interesting time because I needed to find partners out there - leading to some great experiences and some slightly dodgy ones.
I focussed on alpine peaks with snow walking and easy climbing. For this it is essential to be familiar with glacier travel and crevasse rescue - there's no real mountain rescue service out there so in many ways you're on your own. On the flip side, I found that my experience of long days in the scottish hills climbing long days on less than perfect rock/ice was really useful.
Language - the whole thing is a lot easier - and cheaper - if you can speak spanish. This allows you to take local taxis and not chartered tour buses, and to bargain in shops etc. It's also a lot of fun. Good stories of sharing the back seat of a car with a lama.
Gear - take all your own out there. You can buy in shops but it's generally left over from previous climbers and of dubious quality.
Accom - I stayed at Jo's place in Huaraz. A british guy who runs a really chilled out outfit which is pretty climbing-centric.
Guides - if you go to the "casa de guias" in Huaraz they will sort you out with guides, donkeys, transport, chefs and the rest. I would have spent x5 the amount I did if I had done this.
Books - there are a few but the most inspiring I found was something like "climbs in the Cordillera Blanca" by Brad Johnston - great pictures and really positive writing.
In 3 1/2 weeks I climbed Pisco, failed near the top of Chopicalqui, failed fairly low down on Ulta and climbed Hotline on Pucaraju. 4 climbs are pretty feasible if you are organised.
I have no experience of using guides out there.
Have a good one!