I don't have to worry about data use, and I have not used it in SXM but have in Mexico and it worked great. I tried it there before going to India in the fall.

If you are on say Verizon, for $25 you get 100 MB of Data. I believe you can also do $10 a day that gives you a Travel Pass that works off your existing plan. It is not free. Mobile Hot Spot in the US uses a bunch of data, especially if you have several people using it. Skyroam gives you use of 4 devices.

I am not an expert on data use, but I have paid overages noting that I own a company with 10 Verizon phones on one contract.

Cheers,
T