I almost never am able to get the cellular data working on board using the ship's system. I have AT&T, which is GSM-based instead of Verizon's CDMA, and my phone reports that EDGE data is available, which only goes up to 55kbps or so. In other words, it would be *slow* even if it worked perfectly. But it almost never actually works at all, even though voice and SMS work fine almost always.
I would assume but do not know for sure that a Verizon phone would use whatever CDMA's version of EDGE is, and would be similarly slow, and would probably similarly almost never actually work at all.
People mention free WiFi in port, but that's a bit of a hassle. In your situation, I might recommend the $25 int'l data package for 100MB, but NOT the Cruise Ship one. This will allow you to use your phone not only in port, but while on the ship whenever you are in port or near land, which is probably at least half of the cruise. There's no way you'll use 100MB just updating Facebook, web surfing, checking email, etc., as long as you stay away from video uploads or viewing.
For those still reading, the ship-board cellular data we're talking about here is completely independent of the on-board Internet WiFi - that works reasonably well, but you sign up and pay for it on board, rather than through your cellular carrier.
. And some foreign carriers might do this automatically when they see you're roaming from the US. But if you're dialing/texting manually, and/or have a flipphone, the best thing to do is to use the +1 format as that will work in all situations.
