The Belize exchange rate is roughly 2 Belizean Dollars to 1 U.S. Dollar. Paper money is printed in Belize in $2, $5, $10, $20, $50, and $100 denominations. The money is printed rather colorfully and each denomination has its basic color. The penny is the smallest coin denomination and coins are minted in 1, 5, 10, 25, and 50-cent denominations. There is also a 1 Belizean Dollar coin.
All bills have an image of Queen Elizabeth II on the front and have standard security watermarks and security threads. On the other side of the paper money you will see national symbols or pictures of Maya ruins.
It is reported that you can exchange your money at most restaurants, resorts, tour operators, and taxis with little or no service charge. The Belizean banks will make a service charge for exchanges.
American cash is accepted widely but if you are going to use mostly U.S. Dollars then bring small bills as even a $20 bill can be tough to change at smaller restaurants and shops. At the smaller establishments your bill will probably be small anyways.
However the practice of illegal traveler's cheque cashing does continue and is rarely enforced and you should keep something in mind if you are intending to exchange your money in this manner: crime. There are some places, especially in Belize City, that have high crime rates. If you are looking to exchange your money you are in effect broadcasting that you have large bills you want to change or you will have large bills after you cash the traveler's cheque. Use a few street smarts and don't get caught in a dangerous situation.
American Express Travelers Cheques are accepted at most establishments but beware that some places like restaurants will even offer to cash your check for its face value. This is an illegal practice. You can only cash traveler's cheques for their face amount at a bank or a casa de cambio (exchange house). The casas de cambio have commissions that must be paid on the Belize exchange rate so your dollar will get devalued a little.