It's not High Speed, but Amtrack goes from Union Station to Oakland and you can take BART from there.

It's not impossible,. but would significantly complicate matters, trying to get 2 state governments to agree.

Without taking bus part way?

Well, you can take the train from LA to Emeryville and the shuttle bus there should have you dropped off in San Francisco about 20 minutes later (or get off at Jack London in Oakland (the stop before Emeryville and walk to the opposite end of Jack London Square and take the nice view ferry to the Ferry Terminal). Personally, on a cost basis I have not found Amtrak work it for getting from LA back to the Bay Area but it is a pleasant trip to do for the fun of it.

But a big part of why there isn't direct train service into downtown San Francisco, I'd imagine, is that since the lower deck of the Bay Bridge was converted to car traffic from train traffic, all trains into San Francisco are, by definition, dead end routes and apparently there isn't sufficient justification for a train that that stops in San Francisco without continuing on up the coast (I know that when I've taken the train up only one or two cars out of eight are used for Bay Area drop offs).

If the Coast Starlight stops at Oakland Coliseum (I can't remember if it does) then yes you can cross the street and get on BART.

If you get off at Jack London Square, you can take the ferry into the city from the other end of the square (if timing is right). But it is about a 15 block walk (or short cab or bus ride) up to the Lake Merritt or 12th Street BART stations. But on the plus side you can walk through Oakland's Chinatown which is, in my opinion better than San Francisco's for not being wall-to-wall tacky crap.

If you get off at Emeryville you can take the Amtrak shuttle into downtown San Francisco. Or you can catch a Transbay Bus there. Or you can take the free Emery-Go-Round bus (10 minutes once on the bus) to the Macarthur BART station.

You can also get off at Richmond and get right to BART, I believe, but at this point you're probably adding an hour to your trip anyway just from longer time on the train and a longer BART ride.

On the negative side, however, I believe the Coast Starlight gets into town relatively late in the evening (I know it was after dark the times I did it but can't remember if there was more than one daily option) which moots several options and if Amtrak is delayed (not at all unlikely) it'll get more complex.

I know Brendan has taken to coast starlight from Portland to Seattle, so it goes that far. I am for trains, many many trains, it was grand in the UK, they are clean and for longer routes they serve food, real food cooked by people even. I would like to see trucks only carry locally, but then I would like to see anything that can be done in a more local way - don't worry I am not about to go on a globalization rant.

Several years ago we took the train from Union Station to Seattle. It was one of the best trips we've ever taken!

I have heard that the high speed train project is a boondoggle, but after using the London Underground and seeing how usefull it is in other countries like Japan, I feel we need to get onboard that train (pun intended). Plus, I think if I can get to Las Vegas in a few hours- that would be nifty! And I would travel to the San Fran area as long as the tickets are less than flying.

With the state of the oil industry, global warming, road conditions, etc. how much longer can we put off mass transit, boondoggels and all?

You can currently ride Coast Starlight from LAX (Union Station) to Oakland (Jack London) for $68. The downside? It's an 11 hour ride. That said, it's a rather comfortable 11 hour ride where you can get up, walk to the dining car, have a hot meal, watch the California coast go by, even have a bed (for a bit more money)... but it isn't fast. Considering how awful travel by air is it's almost worth it to take the train. Flying LAX-SFO is usually a 4 hour exercise in misery, so I'm thinking if they can get the train time down to about 6 hours it'll be totally worth it.