LA Union Station is probably the easiest big city station on Amtrak to negotiate. If you've seen many movies or TV shows showing an old big city train station, chances are it was LAX!
Amtrak trains use tracks 9 and up (I believe). When exiting the train, follow the crowd down the stairs or ramp. Once in the tunnel, follow the majority of the crowd. They are headed to the train station. (The other end of the tunnel is the bus terminal.)
At the end of the tunnel is the train station.
One more thing about the Surfliners is that coach is unreserved. If there is leaving soon, and you want to take it and not wait 2-3 hours for the next one, you can. There is no need to change your ticket either!
Depending on how you booked your Amtrak trip, BE CAREFUL about having a Surfliner boarding time on an e-ticket, even if unreserved, and then deciding to take a later Surfliner without calling Amtrak or going to a ticket agent first!
If you simply have an e-ticket for an unreserved seat on a Surfliner say, at 7:30 p.m, but decide instead to take an earlier one, you do not need to call or go to an agent. The bar code area will still read out as valid to the conductor as he/she scans your paper.
BUT if you have an e-ticket for an unreserved seat at 7:30 and go for a later train, such as the 10:10, your ticket will not show as valid to the conductor. According to an agent I talked to yesterday, you must call Amtrak or go to an agent and get a new bar code if you op to take a train later than the one booked when you got the ticket.
Yes, it seems silly that this is now required for unreserved trains, but apparently that is the way the system is now set up. When you book online or at an agent for any unreserved train, you have to pick a specific departure time, even if you aren't sure. And the e-ticket turns to stone if you take a LATER train. (Actually, it goes back in the computer as a voucher sum.)
Now, if you have both a reserved and unreserved e-ticket on the same bar code e.g. SWC to LA, connecting to the Surfliner, you need to call Amtrak or go to the agent if you decide to take either an earlier or later Surfliner. This applies only to reservations with both reserved and unreserved segments.