You won't have much trouble taking dollars. In all my travels there was only one port where they didn't take them in the Caribbean, can't atm remember which, but right on the pier was a teller window right outside where you can exchange. I just wanted a coke after an excursion and skipped it due to the line. Also every ship I've been on exchanges currency for the guests, though how much of each kind is limited of course.
I would ask the concerige on day 1 if you need to change from Euro/dollar over and if at all needed they will say which ports dollar might not be adviseable. Most ports are safe-ish but I'd reccomend taking $50 and leaving the rest in your room safe.
11 cruises in 2012, 90 nights at sea visiting 15 countries
8 cruises in 2013, 56 nights at sea visiting 7 countries
Next cruise: None scheduled
PM me if you need a cruisemate for any Europe, transatlantic, or Panama Canal cruises
Date, ship, cost pp