Per Bill Bradley's book Last of the Great Stations, on May 1, 1971 Amtrak had 7 departures and 7 arrivals, depending on the day of the week. In addition to the Super Chief / El Capitan and 2 San Diegans daily, there was the Sunset tri - weekly, a 4 days a week Coast Daylight Los Angeles to Oakland, and a 3 days a week San Diego to Los Angeles / Los Angeles to Seattle train.
Passenger service over Union Pacific tracks was not included in Amtrak's initial planning; only a last minute decision by Rio Grande to stay out of Amtrak moved the San Francisco Zephyr onto the Overland Route between Denver and Ogden.