If you carry about two-thirds of your cash in US currency and about one-third in Mexican Pesos, this should alleviate any monetary transaction problems. You will be able to change dollars to pesos at the Cancun airport or at any bank. Please keep in mind that most fishing destinations are situated in remote locations, far away from banks. The closest ATM may be as close as an hour away by car but there is no guarantee that it will be operational. Always keep small Mexican or US bills on hand for tips, gift shopping, and similar needs. Credit cards and travelers’ checks are most often accepted in metropolitan areas only (It is even possible that some metropolitan hotels, banks, or vendors may refuse your travelers’ checks. Mexican banks are somewhat hesitant to accept travelers’ checks for fear of fraud unless the checks are a brand that is very familiar. Never assume your brand of traveler’s check is transferable as cash in Mexico.
Never leave money unattended in your hotel room or ‘hidden’ in your luggage. Your lodging host will most likely have a safe on the premises for your money and safekeeping items. Always take advantage of this, whenever possible. Since you are a tourist, do not carry large amounts of money on your person if possible. In remote areas, petty theft can be a problem, so always lock your hotel room when occupied day or night. Keep valuables in hotel or room safes and do not leave expensive fishing gear, even muddy flats boots outside unattended.