Most U.S. cell phones can be reprogrammed for use in Belize. You can have that done at the BTL office at the International airport. Last time I checked the cost was around US$50. Then you just have to pay for the cost of outgoing phone service (incoming cell calls are free). In-country calls aren't that bad, but international calls are pricey. As noted, you can also rent a cell phone for US$5 a day from car rental agencies or from the BTL office at the airport. But you still have to pay for outgoing calls, so with rental the total cost is likely to be US$200 or more a month.