My wife asked me about taking a train trip somewhere for nostalgia etc. I checked a few AMTRAK prices, it's not competitive with any other mode of travel. Maybe in Canada.
Yeah, I just, for fun, looked up Irvine->San Francisco. I can get to the Irvine Amtak station in ~10 minutes, and I believe it's free parking there.
Surprisingly not as expensive as I would have thought--about $60 each way. That's pretty competitive with driving it alone--it's about 1 tank of gas for my Ford Flex, which is running low $70s range right now w/ Costco gas prices. Of course, my Flex is a 7-passenger vehicle, so scaling for more people is a huge savings if I'm not making the drive alone.
The downside, of course, is that it's a 12-hour trip. It's 6 hours in the car, and worst case maybe 7+ if you have to cross LA during rush hour. And that there aren't a lot of options each day for timing. The best is showing up in Irvine just before 6 AM and getting to SF at 6 PM, unless you want to do an overnight.
The other comparison is flying. I can fly for <$100 each way on Southwest, from Orange County to SFO, and they've got TONS of flights each day so there is major flexibility in the schedule. It's a 1 hour flight time, and I'd have to add 30 minutes to get to the airport and park, and arrive at SNA 1 hour before the flight leaves. Then if I want to get to downtown SF I'd have to hop on BART from SFO to downtown, which is probably another $15 and another 45 minutes. So actual full travel time is closer to 3 1/2 hours. But it sure beats 12.
The "high speed" rail would likely be much more expensive round-trip, and I don't think it'll come close to beating drive time.
Supposedly it was going to be SF to LA in 2 hrs 40 minutes, but nobody thinks it will actually achieve that for MANY reasons--some technical, some political, and some cost-based: https://www.latimes.com/local/california/la-me-bullet-train-speed-20180729-story.html