ClimbGuy

If you are looking for a SIM card in the US you have two primary carriers to choice from AT&T and T-Mobile.

AT&T has better service and T-Mobile is cheaper.

Since you are asking about data service, 3G service is probably important to you.
T-Mobile: 1700/2100 MHz
AT&T: 1900 MHz

If you have a European phone, it is probably 1900 so you'll need at&t to get 3G.


In order to get the best price you are going to want to get service directly from AT&T and I doubt they have any stores at any airport you mentioned.

Your best bet is to walk into any AT&T store. Since you already have a phone, you can sign up for a contract plan with a 0 month term. Just cancel anytime and your current billing period will be prorated.