If you are interested in the "downtown" Los Angeles area, you might want to buy a Rail Guide from Sam Pottinger's Steel Rails West. He publishes a guide based on local topo maps; he has a link on the trainweb site. Sam also gives 'safety advisories' about the local neighborhoods; some local rail lines pass through some rather depressed and dangerous areas.Unfortunately many of the "city" areas are marred by graffiti, both on trackside structures and the freight cars (wagons). Local UP (SP) switch engines are also tagged, but the road engines for both UP and BNSF are usually 'clean'. Once you get out of town, the graffiti problem is not as severe.
As suggested above, ride Metrolink or Amtrak in the area. Most Metrolink service is on Monday-Friday, but there is some weekend service on lines that are not served by Amtrak.
Santa Barbara is reached by Amtrak, but for Refugio or Gaviota you would need a car, as there are no nearby stations. Those places are north/west of Santa Barbara. I agree with the post from PullmanCo---it is very scenic there, though it can be foggy at times.