If I have an unlocked GSM Android phone, and I want a sim card that will provide data service (preferably prepaid, but postpaid is ok too), then what should I get? Would an AT&T sim and one of their data connect passes work? Do I need a "global" one? (It's a Princess ship, the Sapphire.)

I know it's not cheap, but neither is the ship's wifi, and the service is usually slower than 3G. Thanks for any help!