It's going to be expensive. My girlfriend's friend just got back from a cruise there and a 40 minute phone call ended up costing her $472. Granted that was making a call but If it's anything like how they charge the iPhone, then expect to have a bill much, much larger than normal when using data. Even texting will be expensive.
Personally, I'd recommend logging off the internet and enjoying being disconnected for the time you will be gone but I can't speak for you obviously. 🙂