Best Route: Palmdale to San Diego, avoiding LA

I personally try to avoid the Cajon Pass so the 138 to the 15 would not be my choice. For me, 14 to 210 to the 15 works fine, it is a bit longer but usually has less traffic. You can still get into a mess on the 210 around Santa Anita. Once on the 210, if it jams up, you can take the 605 to the 10 or the 5 as alternates. But I usually just stick with the 210. I really dislike the drive south from the LA area to San Diego as there are so many choke points along the way. Good Luck.