Amtrak to San Diego?

It is reasonably cost effective, cheaper than flying. There are segments with bus or train so make sure you get all train segments and no busses and it will take 13-16 hours. It is really fun and beautiful. You can walk around and there are viewing cars. You have to stop and switch trains at Los Angeles  union station. My husband who is pretty easily motion sick can read on the train without getting motion sick. If you want to test it out you could take the train to Davis its close by and would be a good test before commiting to possibly 16 hours. I recommend the trip. It's fun!

I get car sick and had no trouble on the Amtrak to Reno. Maybe take a test-run on the Amtrak by going back and forth to Sacramento to make sure he is OK.

I took the Coast Starlight to LA with my daughter. It takes a long time but is very pretty. There is also a train/bus that goes via Bakersfield. Train to Bakersfield and then a bus to LA. My husband has taken that, but we haven't. It is faster.

As someone who gets wretchedly car sick I can say I've almost never had trouble with trains, even as a child. Big thumbs up!

I also get super carsick, and did as a child as well. I used to take Amtrak to SLO to visit my grandparents during summer as a kid and never had any issues. I could even read on the train without getting sick (if I was in a forward facing seat) which was far and away the best part :)

Two days ago I left Oakland for LA and then returned via Amtrak's "Coast Starlight" --catch it at Jack London station ONLY.  (If you choose the 'coliseum' station then Coast Starlight route won't appear.)  I chose the 'coach' seating--upper deck.  

My 1st train trip in 30 years.  Wonderful. Scenic. You can walk around.  Get off the train for a few minutes when it stops in San Jose, San Obispo, etc., going I had 15 - 20 minutes to walk around as new passengers boarded.  Returning, because we left 15 minutes late, the off-train, leg-stretchings were 10- 15 minutes. You can spend the whole time in the Observatory car, where the views are even more spectacular. Going there was a young man, in the observatory; he said he'd just been released from prison.  All he had was a pasteboard box with a bunch of Heineken beers..  Blonde, blue eyed, handsome guy, 32 he said.  "chief petty officer" in a former life. He kept drinking & getting louder; I moved away.  In San Luis Obispo, because he got way too drunk, he was diplomatically, quietly, told he'd have to get off the train.  "No problem".  

    Returning, I shared the observatory with an elegant African -American woman, about 65, who was a minister--her parishioners? Soledad prisoners.  Then, 3 years ago, her eldest son was murdered, also a minister, on his way to visit her in the hospital. Broad daylight.  Gang initiation for a teenager who's been in custody ever since.  also there was a B-string, performing comedian, a woman who suddenly knew what her PhD focus would be, another woman, blind, who read braille while I watched her beautiful fingers move across the page.  

      Those who ate in the dining car said the food was delicious.  I brought my own food (you can eat at your seat or Observatory table).  I had a big jug of water--for I didn't want to pay $3 plus for their water, small bottle.  Lots of reading material.  Neck pillow, blanket. 

    My son takes train from LA to San Diego --not sure which Amtrak train makes that leg.  He recommends it highly. 

   Train travel isn't about getting there.  You're already there; already on vacation.  Slow down. Breathe deeply.  Enjoy.

I had vicious car-sickness well into young adulthood. I still get car-sick on buses. Trains have NEVER been a problem, so I think it might be worth a try. Either that or medicate with Dramamine or Bonine.

I can remember those curvy roads to Stinson being such a problem! But no problem on the trains. The tracks are much straighter than the roads. 

As an adult who gets terrible motion sickness, I'd say no way to the train. But if your son is old enough, put him in the front seat of the car with a full belly, water, and Dramamine! And no looking down/reading/playing on his phone. That always does the trick for me! 

PS: to my earlier comments regarding my recent trip on Amtrak (to LA).

   Growing up I got so car sick that my parents wouldn't even tell me we were going to see my grandparents --who lived only an hour away-- 'til it was time to leave. BUT, the one time I wanted to make a bus trip, with all of them, I didn't get sick.  Looking back I feel it was because "I" wanted to do that trip.  My recent experience on Amtrak suggests that it will work for your son as this is HIS idea.  And really a train gives you so much freedom to walk around, look at things, talk with people, and get off now & then. 

   Is it possible for you/him to take Amtrak's  "Coast Starlight" (out of Jack London station) to San Jose one day?  Just try it out.  If you can, spend the night there & then catch it when it comes back the next day? 

    May he soon learn to enjoy traveling.