I’m new in LA and live in the Palisades. Besides the rides in the Santa Monica mountains (Stunt, Old Topanga, Las Flores, Fernwood…), where to go for “flatter” rides. I love climbing and the routes in the mountains are just great but I need to incorporate rolling or flat rides. Is PCH the only option? Trafic is so bad on PCH I can’t resolve myself to ride too much on it…
there are group ride on pch which make it a bit safer…check out la tri club…
Check the river trails. No traffic and LONG rides:
If you have a road bike and you’re looking for a group ride, there’s Montrose. Montrose is a fast paced mostly flat ride with some tough rollers near the end. (You’ll want to climb out of the saddle if you don’t want to get spat out of the back on them.) You can get info at www.socalcycling.com. I’d recommend starting at Trader Joes rather than Descanso Gardens, at least for the first few times.
The LA Tri Club has a calendar full of rides…though many of them involve the PCH, people often work their way from the PCH up through the canyons (latigo, mulholland, encinal, etc.). Unfortunately, PCH is a bit of a necessary evil living in So-Cal.
Another option is to ride south to Palos Verdes. That’s a nice ride, and early in the morning is fairly traffic-free. In the summertime beach traffic can be a bear, especially later in the day.
During the week, there are Tuesday / Thursday LA Tri Club rides that start at 6:30am from 26th / San Vicente in Brentwood. On Tuesdays we do a flat loop around Marina del Rey, on Thursdays we do hills - usually a combination of a hilly circuit around the brentwood country club and a nice 5-mile climb up mandeville canyon. Though be careful on Mandeville because the locals can be a bit testy before they’ve had their morning espresso 
Come on out sometime…and feel free to contact me with any questions!