anallawalla - 3:52 am on Oct 31, 2011 (gmt 0)
Nuttakorn, the pre-paid microSIM from AT&T will only give you 500 MB of data for $29.95, whereas a monthly plan costs the same, as long as you cancel before the end of the month.
I doubt you will find anything useful at SFO that you can't get cheaper at Walgreens in LV.
Check out this thread [forums.whirlpool.net.au], which I used to make my purchase. Given the lack of time, I suggest you plan a visit to an AT&T store. T-Mobile doesn't have anything comparable for visitors. The cheap SIM I have does not have data, hence I am also getting one from AT&T.
Using data roaming to do casual surfing/tweeting/4SQ could cost you several hundred dollars. Been there, done that.