You don't need to change US dollars to Belizean dollars - you can spend the US cash but you'll typically get BZD in change and from ATMs. Check with your bank about ATM and credit card fees and warn the bank ahead you'll be using them in Belize, otherwise the fraud alert dept. may shut down your account. I carry traveler's checks for backup and for places that accept them (I ask ahead). Some places charge a fee for cc and tc use so you should ask ahead about that, too. Happy trails!

I don't know of any ATM's in Belize that dispense US dollars. We live in Belize for several months at a time, and use ATMs to get our cash. Occasionally the machines run out of cash on weekends, not a big deal.

There can be significant discounts for things like tours for paying in cash vs. a credit card. It pays to ask.

I see people standing in line at the bank to cash traveler's checks. It can be a fairly long wait.

US currency is accepted in Belize -- bring lots of small notes ($1, $5 & $10; the larger denominations might not be easy to change in some circumstances (taxis).

Make sure you use all your BZ$ before leaving Belize because it will be difficult to exchange outside Belize.

I use a plastic card to get money from an ATM, but still carry a few traveller's cheques when ATMs are out of order or out of money (yes, it happens), or any other problems with the card (saved me on a few occasions). Never had a problem cashing them and never had to wait long at a bank. Often the queue of people waiting outside in the hot sun for the ATM is longer than the queue inside the cool airconditioned bank. Whatever people say about traveller's cheques, it's still a safe way to carry money.