Travelers' checks are the safest form of money. They can be cashed at a currency exchange ("casa de cambio") and at most banks, by showing a passport or another official identification. No commission is charged.. Keep a record of your check numbers separately from your checks, in case they are lost or stolen. The most commonly accepted credit cards are MasterCard, VISA and, to a lesser degree, American Express. Automatic teller machines ("caja automática") are everywhere in big cities. As a precaution, withdraw money only during daylight hours, in areas with a lot of people, or at malls and banks.