Just look at the schedules, and see where the trains will be at the same time. That is about where the meet will be. On the Sunset Limited, you need to also keep track of the 3 days a week schedule. IIRC, there was a meet between 1 and 2 near Alpine.
You can call Julie/Amtrak and check train status. If one or both of the trains are late, you need to recalculate the meet times.