There is a map in the Robert Hanft book "San Diego & Arizona, the Impossible Railroad" that shows the Los Angeles & San Diego Beach Ry tracks going north along the east side of the bay paralleling the ATSF tracks, then going west through Pacific Beach, then north to La Jolla. I recall tracks paralleling La Jolla Boulevard through Bird Rock area, about a block away to the east. There looks to be a bike path in that Bird Rock area now.
A guess would be Grand Ave in Pacific Beach to PB Blvd, to La Jolla Blvd then next to it, then to Fay Avenue and straight in to La Jolla.