West Coast Specialties does the best metal bodywork and I am sure they can fix the bumper. I have had them do all the metal work on my Boxster and our old Mercedes and all the work was perfect.
However, it sounds like it is in the plastic area - we had Bumpers2Dents do plastic work on my rear Boxster bumper and on our BMW and they did a great job - also very reasonable prices and you can get it done quickly. (
http://www.bumpers2dents.com, located on Convoy street in Kearney Mesa).
Note that both shops are regular Windblown Witness advertisers - it wouldn't hurt to mention you saw their ad if you go to one of these. I think you will be happy with either shop.