It recently became possible to use public transportation (non-Amtrak) to get from San Francisco to Los Angeles. Of course it would take a day and a half, and require staying overnight in Santa Maria, but it is possible. Almost all of the segments are buses, but I present it here because the trip is bookended by Muni LRT & CalTrain on one end, and the LA Metro Red Line on the other. There's also a ~4-hour layover at a hospital on the first afternoon.