Lima and Cusco in particular offer an array of options for going out, from restaurants and bars to discotecas. Most of the places frequented by travelers in the center of town are relatively safe and offer a good time for everyone. When going out anywhere, though, always be aware that spiked drinks, drugs, theft, and assault can be a concern. Be smart and look out for your friends, but don't be overly concerned in comparison to going out with your friends at home. Cusco especially is safe at night for tourists who hit up bars and discotecas.
Beware of Bricheros and Bricheras
A concern you might want to watch out for, however, are bricheros. Bricheros are local men who prey on foreign women. Bricheras, local women who prey on foreign men, are rarer but increasing in number. In general bricheros want to gain your friendship, trust, and confidence. Their goal is both sexual conquest and access to easy money, with the biggest prize being a plane ticket out of Peru so kindly provided by their 'girlfriend' or 'boyfriend.' Many bricheros lure foreigners into thinking they can trust them both with both their purses and their hearts. They may even begin dating. This relationship means something very different to the foreigner and something else altogether to the brichero or brichera. Often a brichero or brichera will have multiple 'girlfriends' or 'boyfriends' at once, taking advantage of all of them both emotionally and financially. Be smart and aware when you go out dancing and drinking.
If you need to take a taxi home after a night on the town, don't go alone. During the day it is relatively safe to take a taxi alone, but at night most Peruvians try to go in groups. Women especially should not take a taxi alone at night.