Check the rail monitoring thread for some info on monitoring while on Amtrack. Then check the route and load up some local freqs from the DB for along the way. I recall seeing a link to a rail page with the frequencies used in each segment of the various Amtrack segments.
If you have a 396 or 500 and didn't blow the preloaded systems away (someone is bound to have the files if you did), you have the highway patrol for each state. May take some tweaking to get them into a usable order, but that's part of the fun (?) of traveling.
My last long rail trip was when I was 13. My family and I went from SF to Denver on the California Zephyr. No scanner in those days, but it was still a thrill.
How are you traveling to LA (I know by train, but a coach seat or a sleeping compartment). If you are in a sleeper there is a power plug available. You could set your scanner on the table plug it in and use the cheap antenna that came with the 996 to listen in.
If you are in a coach seat that would be a bit more difficult.
Check out the options. You could still listen in.
I also hope you're travel timing allows you to take the Sunset Limited. I just checked Amtrak's site to verify what's available. NATURALLY you have to act like you're making a reservation. First day I picked was a day the Sunset didn't run and I could go to LA by way of Chicago to LA, Chicago to Portland to LA or Washington DC to Chicago to LA (SAY WHAT???).
Oh yeah, there is an outlet and a table in the small sleeper compartments, but not mentioned for coach seating. If you can afford it, upgrade to a roomette with shower access. After two days on the train those down wind would appreciate it.
Check camera stores, Battery Stores, radio Shack, etc., and look for portable power sources and cigarette lighter connections. You should be able to set up a "scanning station" in your briefcase or back pack.
Also, depending on where you sit (suite, lounge, coach) there may be a 120 volt AC source nearby. If so, all you need is the wall wart, possibly an extension cord or power strip, a right angle BNC connection, and a rubber ducky. Place near a window, and you should have more listening than you want, especially while passing through the RR intersection areas, such as in Dallas/Ft. Worth.