you might arrange to get off the SWC in Fullerton to wait for the Surfliner. It's the last stop on the SWC and you go about 25-30 miles north to LA. You'll be passing right back by it on your way to San Diego. Of course if you want to see Union Station then you'd have to go to LA.
When I originally booked my reservation ABQ-SAN I wanted to go from Albuquerque to Fullerton to San Diego. But the Amtrak agent on the phone checked, and said changing in Fullerton would be an "
illegal connection" unless I stayed over night in Fullerton.
Thus (?) I booked ABQ-LAX-SAN.
And, as the person picking me up in San Diego doesn't like to get up too early (i.e. before 10 AM) I think I'll go on to Los Angeles and check out the lounge.