If you can make it to Del Norte County, you will not regret it!
Bearflag, “Difficult to folow”–about PCH in L. A. County–is hardly the word for it. You can follow the coastal road southbound into Santa Monica, but, depending whether you turn off on the California Incline or not, you may wind up getting totally lost!
You can turn left onto the California Incline, which becomes California Avenue; you can turn right onto Lincoln Blvd., one block past 7th Street. But if you continue on the highway along the beach–according to the Thomas Guide that street is named Palisades Beach Road in Santa Monica–you’ll wind up on the busy Santa Monica Freeway (I-10), heading for downtown Los Angeles! :eek: (if you do, just take the first exit, which is Lincoln Blvd.) 
Lincoln Blvd. runs through Venice and into Marina del Rey, and ascends a hill into Westchester, where it merges with Sepulveda Boulevard which, of course, runs southward generally from the San Fernando Valley. (If you’re going northbound on Lincoln Boulevard, you’ll wind up at the T-intersection with San Vicente Blvd., which has no connection to PCH.)
Sepulveda becomes Pacific Coast Highway when it leaves Manhattan Beach, south of the airport area. (In fact, for several blocks it’s the boundary line between Hermosa Beach and Manhattan Beach, so one side of the street is Pacific Coast Highway and the other is Sepulveda Boulevard.)
Then Pacific Coast Highway continues south, then generally east, in south Redondo Beach and runs through Torrance, Lomita, Harbor City, Wilmington, Long Beach, and clear out of L. A. County, continuing into Orange County at Seal Beach.
The Sepulveda Blvd. in Torrance, running eastbound to Long Beach (where the name changes to Willow Street), is not the same as the Sepulveda mentioned earlier.