Once you have more than a private you can't come in on a J1 to instruct either.
So you'd need to commit to instructing once you started your FAA CPL / IR at a school which did J1 sponsorship.
I'd also remind you, if you want to work in JAA train JAA.
If your set on FAA then make sure you instruct to gain experience before converting as it is normally a lot more costly than people anticipate as they go over hours.