Check with the IATSE(International Alliance of Theatrical and Stage Employee's) locals.
I'm not sure what you do or what local you would need to contact but the IATSE covers all the crafts, camera, grips, propmen, electrical, art, special effects, etc.
For directors or asst. directors it's the DGA (Directors Guild of America)
On camera is't SAG or SEG
(Screen Actors Guild, Screen Extras Guild)
The easiest way to contact any of them is to go to their website for L.A.
If you are looking for a PA or intern type position then you have to contact the local production companies..
A good source of information for the west coast would be The Hollywood Reporter
Most filming down here is location shoots based out of Hollywood. I have have seen a local production company still filming a UPN tv show