Replace the rotors.
The glazing is probably your problem.
Good info here: http://www.stoptech.com/tech_info/wp...rakedisk.shtml
It wouldn't surprise me if the mechanic just slapped the new pads on and didn't turn the rotors. If it's only been a few months, you should still be able to see the cross-hatching on the discs from the "turning", unless you've driven a ton of miles since.
FWIW, as long as it stops well, you can live with it (squeeling). I always adjust the rears when I do front brake jobs. If you don't, the fronts do ALL the work (they do 80% of the work anyway) and heat up, glaze, etc. The rear's self-adjusters don't always "self-adjust" if you don't use your parking brake frequently. If you back up and brake vigorously several times, it will tighten the rears (if the adjusters aren't frozen).
Cliff's notes: Rotors are glazed, replace them. Rears probably need adjusted too.
Welcome to R-F.