Here are some good routes I found:
"Quahog Sub": A route based on SoCal but is very fictional.
"Baldwin Park": More of a railfanning route rather than a full-blown route based on a town in SoCal.
"BNSF Central Valley Subdivison": One of my personal favorites. A route that takes place in the California Central Valley. It goes from Laton, CA to Corcoran, CA. 35 miles in length to be precise.
"Los Angeles Junction Railway": A small route of some trackage from the real-life railroad.
"Pomona, CA": A railfanning route of a station in a city in Orange County, California.
"9th Street Modesto Ca Streetrunning Diorama": A 3 baseplate railfanning route by me of a now defunct branch line in Modesto, California.
"Industry, CA": A small railfanning route of a fictional California inspired place.
"Mojave Sub Divison - TRS19": A recreation of the original route by JR upgraded by hiawathamr. Please keep the old route for the new route to work properly.
Where to find routes:
"Quahog Sub":
https://www.trainz.net/index.php?/files/file/133-quahog-sub/
All the other route are on the DLS. Have fun! (Warning: Some routes like the M&ET route are not all up to today's standards or are not the best, so be warned.)