Read up on Lonely Planet's guide to Peru.
Especially interesting is the thread, "Outbreak of Bubonic plague in Peru" (!)
I would personally consider 120 roll film to be an alien concept in Peru, in fact anywhere in South America, and might be best to take as much as you can physically take — and keep watch over, with you. It would be hard enough to find a watch battery (or try a 2CR5 battery...). Most of my friends who have been there (chiefly to Machu Picchu where some truly atmospheric studies have been shot) with MF have taken their own (B&W) film with them.