One of the best pieces of advice I could give to someone travelling to Grand Cayman would be to change your money daily. Most places do take American dollars but VERY FEW of them will give you change in dollars, so you're left wondering if you're getting ripped off or not. Your best bet is to change your money from dollars to Caymanian dollars (CI$) at your hotel. You can do it at the bank for a price, but the hotel will normally change up to $100 for you a day for free. This is the best thing you can do, you can get about CI$ 80 for $100, just be careful, you can’t change your CI$ back into American dollars. It's still best to pay in Cayman while you're there, just easier to figure out and you don’t have to do the exchange in your head. Be careful with the cabs, some of them will overcharge you. My friend and I could go PAST Georgetown for $11, whereas earlier in our trip we went to Georgetown and were charged $20. We learned quick, though. There's also a bus for $2 that you can take down the "7 mile strip." Renting a car is an option, but I wouldn’t do it - there IS traffic in Cayman and driving on the other side of the road if you're American can be tricky.