It is best to arrive to Peru with cash for your trip. Make sure the bills are in good condition because many places wont take worn or ripped bills. The places in Cusco that will give you the highest exchange rate are money changers on the Avenida Sol at the intersection of Ayacucho. In Arequipa it is on Calle Jerusalen, and in Huaraz it is just off the north side of the Plaza de Armas in the passageway going to Parque Ginebra.
Using Credit Cards on a trip to Peru?
While there are good restaurants where you can pay with a credit card, anything more local only accept cash. Also, if you buy a souvenir like an alpaca sweater, don’t expect them to take credit card either unless it is a more expensive boutique store. Out of the city centers, in villages or small towns you won’t be able to use credit cards in Peru
Using ATM or withdrawing money in Peru?
The ATMs only let you take out $140-200 USD at a time per transaction, the ATM fee and your bank fee will probably be around $7 total per withdrawal. Keep this in mind and if you have to take out a sizeable amount it is better just to bring it in cash and keep it close to your person.