Good points on using credit cards, but keep in mind, you will still need a fair amount of cash. We pay everything on credit cards that we can, and I still budget about $30-50 per person per day in cash. Mooring fees, cabs, departure taxes, places where "the credit card machine isn't working", dropping trash, etc. Also, it's often just easier and more convenient to be able to pay in cash when you're just buying a drink or two, or when a place is especially busy.

Net, net, good to pay with credit cards when you can, but you gotta have greenbacks too, no matter what.