Your mobile phone must be of GSM status and able to carry signals at 1600 megahertz. The typical service providers that offer phones that would work in Belize are T-Mobile and ATT
If so, yes as above, will work with most networks if you tell them before (mine is O2). Most calls and texts come through, but not all.
If you want to use a local SIM, check the phone is unlocked (many UK ones are, most US ones aren't).BUT most local SIMS don't accept international texts! Don't ask me why! It's mad.
BTL will now be offering internet on cell phones provided that they onfigure to its systems. It will also include the sending of international text messages as well as internet, email.