I haven't ventured to Monkey Island myself (although now I'm intrigued), but according to my research it seems to be a tourist attraction; however, an interesting, fun attraction for visitors who love wildlife. It is a sanctuary for monkeys who have been treated poorly in other situations, and the monkeys have been placed on this island for protection. You will probably have the chance to see monkeys during your trip to Peru whether you go to Monkey Island or not, but if you are especially keen to see all sorts of types of monkeys, it may be a good addition to your vacation!