Yes the GT-i9300 would because it's the unlocked international GSM version.
He's asking about the SCH-i535 which is the US Verizon version. Verizon is a CDMA carrier, but the phone has global capabilities (GSM). There's not much info about people using the i535 on AT&T's network, but there is a spattering. If I was him, I'd try popping the SIM in the phone and see. If it doesn't work, sell the i535 and purchase the SGH-i747 (AT&Ts version) with the proceeds.