You should not need to change money in Grand Cayman, since U.S. dollars are readily accepted, though you may get some change in Cayman dollars. ATMs accepting MasterCard and Visa with Cirrus affiliation are readily available in George Town; you usually have the option of U.S. or Cayman dollars. The Cayman dollar is pegged to the U.S. dollar at the rate of approximately CI$1.25 to $1, and divided into a hundred cents, with coins of 1¢, 5¢, 10¢, and 25¢ and notes of $1, $5, $10, $25, $50, and $100. There's no $20 bill. Traveler's checks and major credit cards are widely accepted. Be sure you know which currency is being quoted when making a purchase.
Prices throughout this guide are given for adults and unless otherwise indicated are in U.S. currency. Substantially reduced fees are almost always available for children, students, and senior citizens.
It's a good idea to inform your credit-card company before you travel, especially if you're going abroad and don't travel internationally very often. Otherwise, the credit-card company might put a hold on your card owing to unusual activity—not a good thing halfway through your trip. Record all your credit-card numbers—as well as the phone numbers to call if your cards are lost or stolen—in a safe place, so you're prepared should something go wrong. Both MasterCard and Visa have general numbers you can call (collect if you're abroad) if your card is lost, but you're better off calling the number of your issuing bank, since MasterCard and Visa usually just transfer you to your bank; your bank's number is usually printed on your card.
If you plan to use your credit card for cash advances, you'll need to apply for a PIN at least two weeks before your trip. Although it's usually cheaper (and safer) to use a credit card abroad for large purchases (so you can cancel payments or be reimbursed if there's a problem), note that some credit-card companies and the banks that issue them add substantial percentages to all foreign transactions, whether they're in a foreign currency or not. Check on these fees before leaving home, so there won't be any surprises when you get the bill.