I am looking for schools that offer jobs after training
A job offer is only an offer, I'd be cautious with any school that offers a job.
There is no real way they can guarantee a position for you.
The job market for flight instructors is pretty much saturated right now and will be for a while to come.
Experienced instructors are sticking to their jobs and not moving on to the regionals/airlines.
Are US flight schools saving jobs for locals ?
I don't think so, see above.
Issuance of J visas is supposed to stop in June 2010. Is the US government already curtailing these ?
Probably not, the school in question may no longer be authorized under the J-1 program.