In San Diego I would hang around the station area. During the day most of the traffic is passenger. Around noon there's a freight that rolls out of San Diego heading north.
Riding the Pacific Surfliner northbound out of Los Angeles can be a fun ride. It's also known as railroad Westbound. When SP owned the trackage, their headquarters where in the Bay Area (San Francisco), so everything heading towards San Francisco was Westbound and everything heading away from San Francisco was Eastbound. At Burbank Junction the mainlines split, one going thru Bakersfield is the old Saugas Line, the one going thru Santa Barbara is the Coastline. From Burbank Junction to the Northridge area the train travels at 79mph, making station stops at Burbank Airport (now known as Bob Hope Airport), Gemco (the old General Motors plant in Van Nuys---now a shopping center, with an Amtrak Station). It's a straight run from Burbank Junction to the Northridge/Chatsworth area, the tracks will run in a Northwest direction. At Chatsworth, there's kind of a sweeping curve between DeSoto Ave. and Lassen St. where the tracks will head straight north for a mile or so. The siding at Chatsworth has been lengthened from 4,056 feet to 7,160 feet, so there are two tracks that the tracks can use to make their station stop at. On the left hand side of the train at this point are the Santa Susana mountains where the San Fernando and Simi Valley's are divided. After leaving Chatsworth, the train will make a left hand turn passing thru 3 tunnels. Tunnel 28 is 537 feet long going underneth Topanga Canyon Blvd., followed by Tunnel 27 at Chatsworth Park (924 feet) and finally Tunnel 26 (7,369 feet long) leading out towards Simi Valley, where there's another station stop. The closest freeway is the 118.
Between Burbank Junction and Chatsworth is the San Fernando Valley section of Los Angeles. Mostly residental, with a lot of business. There's about 1.5-2 million people living in the Valley.
As you travel out of the three tunnels, you'll be in Ventura County and in the City of Simi Valley. Mostly residental until the west end. The scenery starts to turn into more of a business area.
The tracks are dispatched by the Metrolink Valley Ventura Subdivision Dispatcher from Burbank Junction to Las Posas (Moorpark area); from here it's dispatched by the Union Pacific Dispatcher (DS50). There's the usual Amtrak's, I think 13 plus the two Coast Starlight's, Metrolink trains and nine UP freight's.
In the Moorpark/Oxnard area it's more farmland than anything else.
At the Northwest end of Ventura the tracks head along the Pacific Ocean for about 110 miles up to Devon. Highway 1 heads inland at Gaviota east of Vandenberg Air Force Base, while the trains with remain along the coastline and to the west of Vandenburg. When the Air Force is going to launch a miscle they notify the railroad so the trains will stop until after the event. Also, it's close to the time of year when whales and dolphins are migrating in the twice a year trip between Mexico and Alaska, which can be seen from the train.
In Santa Barbara the train stops a few cars away from StateStreet; the tourist section of Santa Barbara. One block away is Sterns Warf, which has some shops and resturants.
In san Bernadino, this is BNSF territory, along with Metrolink. Union Pacific's big yard is along I-10 in West Colton, a few miles away, between Pepper Ave. and Sierra Ave.
This is the main way in and out of Los Angeles for BNSF. To the north of San Bernardino is Cajon Pass. UP has trackage rights on the BNSF as well it's own set of trcks between West Colton and Bakersfield. In this area a railfan can see 4 trains in a 5 minute period of time (figure about 50 trains a day) plus Metrolink in and out of San Bernadino. It's both residental and business around this area.
Three of the better known railfan spots are in this general area. Beamont Hill, which travels between West Colton along I-10 and Indio and on into Yuma. Cajon Pass which is between Barstow and San Bernardino. Finnally Tehachapi, between Mojave and Bakersfield. Lots of traffic in this area. Beamont Hill sees 6,000 ton hot shots and 14,500 ton drag freights and evrything in between.
Enjoy your trip out here later on this summer.