I'm looking to take a train one way from LA to San Diego. I think there is more than one train that does that route. I was looking at the Pacific Sunliner. But then I saw mention of the 500 and 700 train?? What is the most economical and timely of my choices. Thanks for the help!

$35 fare are available on amtrak.com regardless of the day. Trains depart every 1 or2 hours all day, so take your pick.

Do I need to buy tickets ahead? Do the trains fill up?

It is much easier to buy your Amtrak tickets on your phone using the app. You get a QR code to show the conductor when he/she is collecting tickets. Ticket windows can have a line to wait through at staffed stations. At home using your computer and a printer, you can also print out the ticket with a QR code.

No, these trains do not fill up.

The train occupency can depend a little on time of day and day of the week. I visited my parents on a Tuesday when they were visiting San Diego once and Union Station to end of line definitely had a lot of room. When I'd take the 9am train down to Irvine on a Saturday, I almost also had to sit with someone. The way back at night was typically more open.