US dollars (paper money, not coins) are freely used in Belize (and most businesses would rather receive US dollars than Belize dollars). So, no need to exchange money at the bank or elsewhere.
Do bring smaller denominations to avoid problems getting change.
Banks will give credit card advances for $5-$10 USD per advance. If you use a Visa debit card, you can avoid cash advance interest charges, but it has to be a Visa or Mastercard debit card, a bank issued card won't work in Belize. ATMs that will process credit, debit and ATM cards issued outside Belize are not available everywhere, and the ones that supposedly do, don't always work. Therefore, if you really need cash, make sure to get to a bank during banking hours (usually between 8 a.m. and 2 p.m.) so that you can get a cash advance inside the bank if the ATM doesn't work (or if the banks near you don't have international ATMs).
Locations of international ATMs are: Orange Walk, Corozal, San Pedro, Belize City, Belmopan, San Ignacio, Dangriga, Placencia and Punta Gorda.
Belize banks will give generally NOT give you the official exchange rate of 2:1 when cashing traveler's checks -- sometimes not even for US dollars! However, you don't need to cash your traveler's checks or exchange money at the bank, because local merchants WILL give you a 2:1 exchange rate.
American Express Traveler's Checks are the most commonly used traveler's checks in Belize. When using a traveler's check, don't fill in the date or the name of the merchant, otherwise the merchant will have to deposit the check and the banks hold them for 40 days before making the money available. (If the date and the name of the merchant are not filled in, the traveler's checks are used pretty much as cash and somehow eventually find their way back to the States where they're cashed and deposited in someone's account, somewhere.) Also, make sure that your signature looks like the signature you used when you purchased your traveler's checks.
Visa is the most commonly accepted credit card, American Express and Discovery aren't accepted by very many businesses. MasterCard is now only accepted by larger businesses that have an electronic credit card processing machine. (MasterCard imposed a $0 floor limit on all Belize businesses, which means smaller merchants that have to call their bank for a credit card approval won't accept MasterCards -- especially during non-business hours.) Also, many businesses charge a service charge for the use of a credit card, so make sure to ask first (the service charge is usually 5%). Note: we do NOT add any service charge to credit card transactions.
Most credit card issuers except Capital One charge a currency conversion fee, and some charge a currency inversion fee. This may be true even if a Belize merchant actually processes your transaction in US dollars. The merchant has no control over whether a currency conversion or inversion charge is assesed on a transaction -- this is entirely a function of the terms of your credit card issuer. If you don't know whether your issuer charges a fee or how much that fee is, check with the issuer -- and if you time, it may be worthwhile to get a credit card that doesn't charge currency conversion fees to use for your international transactions. (more information)
If you absolutely must stay in touch by phone with home or office during your Belize vacation, please consider renting a satellite phone and bringing it with you, or renting a cell phone from Belize Telecommunications Limited (BTL) at the International Airport, because even if your cell phone company tells you your cell phone will work in Belize, it may not. You'll have to buy pre-paid phone cards to use with the cell phone, but the rates won't be quite as high, and you'll also know exactly how much you're spending.
Please note: you will need a pre-paid BTL phone card to make local calls within Belize from pay phones. You can purchase a card at the international airport and from local merchants who display the BTL phone card sign.
Internet: Internet cafes and Internet connections at resorts are extremely common throughout the entire country of Belize, so you shouldn't have any trouble staying in touch via email during your trip. Note: Skype is blocked by BTL and doesn’t work well on satellite systems used by resorts and lodges not served by BTL. So, don’t plan to rely on Skype, MagicJack or other similar VOIP services. (Some Internet cafes are now providing the service through cable Internet, but don’t plan to rely on finding an Internet café that does offer VOIP.)