No matter what, TURN OFF DATA ROAMING! Seriously, easy to do, and a nightmare if you don't. I rememeber a good news story about a guy in Mexico
, his kid decided to stream a full HD movie
over data. 11, 000$ bill later...
Vacation Nightmare: Family Billed $11,000 For Streaming Movies | ABC News Blogs - Yahoo!
Turning off data roaming prevents that sort of excitment.
It's nasty anyways since carriers buy from each other at bulk rates, after canceling out the usage from both sides and ding their customers at 10x or more of that.