American dollars are best. Travelers checks in USDs are best. And opening a bank account can be difficult because you need two letters of reference from your bank and a letter of reference from a local known person. Credit cards work well at resorts and bigger restaurants if you want to preserve your cash.
The usual Visa, MasterCard, and some American Express. Discover isn't widely used. Also, be careful of Bank Debit Cards because they take money out of your account immediately. This has gotten people in trouble.