iPhone 4S and prepaid in the US

I'm stationed in Germany, but go back to the states a couple of times a year. I used to be able to suspend my ATT account, then turn it on while in the states. Now I can do that once per year (last time I checked). I have a factory unlocked 4S, so I wonder if it is possible to get a prepaid phone and data SIM card from ATT or any one else. Has anyone done this? I know I can in most countries that I travel to, as long as they have some sort of data on cell signal system. ATT said to get a prepaid phone, but I'd rather use my iPhone while I'm there, as I do around Europe and other places I travel.