I just looked up the specs for the N7000, and it seems it should work fine on the AT&T SIM. It will also work on the T-Mobile SIM, but will only get 2G/EDGE data speeds. If you have the paperwork on it please confirm that on the 3G/HSDPA frequencies it states:850, 900, 1900, 2100. AT&T uses the 850 & 1900 bands.
I'm currently using the Straight Talk AT&T SIM and am pleased with the service and performance. One thing to point out is that ST is stingy on data on the AT&T side. If you use too much in one or two days, or overall for the month, they will throttle you and eventually cut you off if you keep it up. Their ToS specifically prohibits streaming and tethering.