LSC, I'm a Canadian that visits San Pedro regularly. Travelers Cheques are a huge pain in the butt. Don't bother. Bring some US cash from home to get you started, along with your regular ATM card. My BofM card works just fine at Belize Bank. Can't remember the exact amount of BZE dollars it dispenses but I'm thinking the BZE $ maximum for each withdrawal is $500 BZE, which is equivalent to $250 US. I generally chose to do a double withdrawal just so's not to have to go back to the ATM machine quite as often. Like I said, for some reason, can't remember exact amount, maybe it is only $250 BZE, which might be why I do two withdrawals.
Everyone takes US $, but will give you change in BZE $, which may be a bit confusing initially, especially if you've been drinking a few Belikin or rum punches. Just to help mess you up a bit more, sometimes the change comes in a combination of BZE $ and US $. But very soon, you will catch on and it is often better to use the BZE $, as soon and as often as you can.
Just remember, unless you are planning to come back to BZE soon and/or often, try not to accumulate too many BZE $ towards the END of your trip. As you come up on the end of your trip, start asking for change in US dollars, whenever possible. At the last few days of your trip, try to spend up all your BZE $ without accumulating more BZE change.
Another thing you might find helpful, is to put away the money for your exit fee (that is unless it has already been included in the price of your airline ticket).
Have a wonderful trip.
A fish and a bird can fall in love, but where will they build their nest?