Most restaurants and stores near Plaza de Armas (the main square) take credit cards and debit cards. Its always a good idea to ask if they take card first before trying to make a purchase. It is also a good idea to check with your bank or credit card company about international fees. Some cards do not get charged additional fees. You will also want to make sure to let your bank know where you will be so your card does not get deactivated.
There are two ATMs in Cusco you can use to make cash withdraws: Multi Red and Global Net. Note: There will be pretty big fees charged by both the ATM and likely your bank. For this reason, we recommend bringing cash that you can exchange here in Cusco.
There are several exchanges on Avenue El Sol, the main street of Cusco. We can show you were you can go to exchange money and help you with the process. Make sure to bring clean, unbroken bills. They must be in the best condition and new is preferable. Note: Banks and Airport exchanges give the worst rate. Please avoid using these.
It is best to be as close to Plaza de Armas as possible. One neighborhood we recommend to get an Air BnB in is San Blas. The closer you are to Plaza de Armas, the better!