@matigo Prepaid in the US is not nearly as convenient or as cheap as it is in, say, Thailand where I was able to buy a $10 SIM from a Kiosk that included call credit and 3GB of high speed data which expires in a week.
T-Mobile has a travel SIM deal [prepaid-phones.t-mobile.com], which is $30 for 2GB of high speed data for 3 weeks. Don't believe AT&T has a short-term tourist plan.