I was in Belize last week, San Pedro on Ambergris Caye. We all used cash U.S. dollars with no problems. The exchange rate is 2 Belizian dollars to 1 U.S. dollar but the Belizian prices were usually twice as high as in the U.S. so you really don’t get any deals because of the exchange rate. All of the businesses and vendors take US dollars but only give change in Belizian dollars.
One person said their credit card would not work in the ATM. I only used my credit card once and my credit union only charged me 1 penny on the dollar for the exchange, not a bad deal.
Before we left our group leader, who has been to Belize many times, recommend using only cash or travelers checks because some divers on previous trips had had their credit card numbers stolen.
As an aside, the diving off Ambergris caye was a big disappointment. The reef has been heavily overfished. Most dives were spent drifting over coral with an occasional fish swimming by. The only exception was in Hol Chan reserve, not a lot of variety but there were lots of fish, morays, eagle rays and sting rays plus a few nurse sharks.