I would allow 2 to 3 days from SF to LA, depending on what you want to see. In that vehicle, I'd plan on about 18 mpg - $4 a gallon may be high but better safe than sorry. Gas prices are usually pretty much the same on the whole west coast (CA-OR-WA), but if you have to get gas in a remote area, you may even see $5 a gallon, plan stops accordingly. An example is in Big Sur, the one station I saw there is so expensive they usually don't even put out a price sign. Fill up in Monterey and you should have enough to make it to San Luis Obispo.