re: Grand Cayman Recs....

Every place we went took American dollars, but gave change in Cayman currency, so we never exchanged any cash. Just watch out for them short changing you. We never had it happen, but were told to keep an eye out for it. Most places also take a credit card, so whichever you're comfortable with. You'll need cash to tip fishing guide and sting ray city guides, assuming you booked a charter for both, but they also gladly take American dollars.

If you weren't already prepared, everything there is expensive. More expensive than other Caribbean islands I've been to.