Sounds like the best thing for you would be to print out the Amtrak schedules for the Coast Starlight and Pacific Surfliner trains. When you get tired of riding the bike, hop on the train and head to San Diego or Los Angeles. You'll pay a bit more booking the train last-minute, but my guess is that you wouldn't have a problem getting a ticket on short notice. I took the Coast Starlight north on a weekday and it was relatively empty...