Last month took a 2 week cruise through the Caribbean aboard the Sea Princess. There was no Internet service available in any of the cabins. There was an Internet cafe on board with 14 stations. There was also a bar adjacent to the purser's desk with another 6 Internet stations. The Internet service was available for $10 per 30 minutes of usage. You simply swiped your cruise ID card and it was charged automatically to your room. Since I took my own computer (my trusty PowerBook G4) I could sign up for a wireless pass usable anywhere in the Atrium adjacent to the purser's desk. There were 4 levels in the Atrium where you could use a portable, and each level had many comfy chairs and tables. The charges were the same, but you had to buy a separate Internet Card for each 30 minutes you used their wireless service. This was a little cumbersome since the time on a particular card would run out half way through sending/receiving e-mail. You would have to go back to the desk and buy another card. And each card had a different usage number and password... not too bad if you bought multiple cards from the get-go. My only complaint was the speed of the onboard Internet service - it was dial-up speed. I had my Cingular service cell phone with me so I tried using BlueTooth at every stop. It only worked in the Bahamas and on Cayman Islands.
Most of the islands we visited had Internet cafes near the port with real high speed service. They all charged nearly the same for Internet connections - about $2.50 for 30 minutes. Grenada actually had a free hotspot inside the port terminal... But I never bothered to come back ashore with my computer. Lugging it on and off is a pain, and some places it created a bit of hassle with trying to get through local customs when coming back to the ship.
Isla Margarita, Venezuela had a blackout on Internet service. Even the cruise ship's Internet service was blacked out until we were back at sea about 50 miles out from the island. I guessed it was another of those amenity deficiencies thanks to President Chavez.
One last word - if you have a modem and want to use your dial-up connection, be prepared to waste a lot of time chasing down phone cards that can only be used on some phones. And many of those phones do not have data jacks in the phone sets. Fortunately, all of the telephones in the Caribbean adhere to the RJ-11 connector standards. 'Til next time...