The official currency in Mexico is PESO. You may change your money into Pesos at a number of locations in Cancun at an estimate exchange rate between 11 to 12 Pesos for 1 US Dollar. Traveler Checks, U.S. Dollars and credit cards are accepted by almost all businesses in Cancun and the surrounding area. If you do exchange money do so in small amounts as you so you will be able to spend all of the pesos before leaving Mexico.

You can also get Pesos at the ATM machines, they charge a surcharge to dispense cash. Gone are the days of no fee ATM's. The surcharge is about 7.50 Pesos

If you plan to use your credit card it is necessary to call you bank or credit card company and let them know that you are coming to México because many credit card companies does not accept foreign charges to protect their clients so it may happen that once in México you try to use your credit card and will not get an authorization or will be reject by terminals.