jailbreakme.com doesn't active the phone unfortunately. It will only jailbreak the phone so you can install third party apps and unlock the phone. It only works on 1.1.1 though.
if the phone is unlocked and your using on a gsm network then yes it will work try to get a phone that isn't 1.1.2 otb as that cant be unlocked yet but you could get turbo sim for it but those are hard to get i hear