You are right. It can be dangerous riding on Pacific Coast Highway. Around traffic areas and near Pepperdine/Malibu, where there are rock slides and the rocks spew onto PCH/shoulder, it forces the biker to briefly go out from the bike lane and around the rocks/barriers. I've heard of several riders getting hit by cars from behind. One rider from a local cycling club was killed.
Traveling in a group (you're more visible) and riding single file is pretty safe. Obeying the law of the road too.
Well, that was during my younger college years when I had more courage. Riding my bike from Westwood to Pepperdine on a Saturday morning, having an overpriced coffee and scone at Starbucks in Malibu, and riding back to my apartment again. The ocean view was great on sunny days. Mountain biking in the Santa Monica Mountains/canyons was nice too.
Now I'm older and wiser...
...I don't go to Starbucks anymore for their pathetic coffee. LOL!