It isn't easy to convert your money back into US. You need an exchange control permit and need to have a valid reason why you want the funds converted. Belize has a limited amount of US currency on hand which is used for the purposes of purchasing goods that are then imported into the country, or to pay off foreign debt etc. So to get a permit citing that you wanted to take advantage of the high interest bearing accounts in Belize dollars and now want to rake in your profits and repatriate your funds overseas might not be a valid reason to get an exchange control permit approved.
Ok, Lets say I won 7K BZE at thr Princess and am flying back to the states and now I want it changed into US Dollars. I have my return ticket and am standing at the booth inside wanting to exchange it. Are they going to or not?