In case you didn't notice on Jayson's link to A&I, their main locations are in Hollywood (different locations for different services) plus labs in Santa Monica and downtown LA. The Santa Monica lab only does E-6 on-site, everything else gets shuttled to Hollywood, but the turnaround is pretty fast. For a long time they were the gold standard in town, but many glamour/celeb shooters now also use:
All of the above are in Hollywood. There's also my lab, which is less expensive than all of the above, (and which is also Playboy's lab in LA):
Santa Monica Color Lab
1669 19th St
Santa Monica, CA 90404
You should contact them all if price, location or operating hours are important. All of these have various extended and weekend hours to accomodate pros. There are dozens more, but I think these are what you want.
Andy Pearlman Studio