Don't assume that you will be able to do that, there was a recent moratorium on changing Bz dollars back into U.S., and even if you can, the bank rate is close to a 10% surcharge. You get the best exchange rates at the border. Every business here accepts U.S. dollars, and if you bring small denominations, you probably wont have to deal with large amounts of Bz dollars. Bring lots of 1s, 5s and 10s. $100 bills are sometimes difficult for retailers to make change for, and most of the time they don't hve a surplus of U.S. cash to hand back.