Oh it isn't? I guess I just assumed it was, my family went from San Fran to Carmel for a day trip and that was nice from what I recall and just heard other nice things about the drive. Next time I'm driving out in Cali though I want to be driving through Yosemite
SF to Carmel is a pleasant drive, particularly if you go through the forest. After Carmel is where it really turns good, though. The problem is that once you get around San Luis Obispo it starts to look like mile after mile of farmland, and there's no place to go except backward or forward for hours. It's also not a drive you want to do in one day, so you have to crash somewhere along the way in one of the less scenic parts. Things don't turn pretty again until around Malibu, by which point you're damn near in LA anyway. At least that's been my experience. I guess my advice would be to spend a day exploring Big Sur before heading back North and crashing in Carmel. Then just take the interstate on to LA.
Dark Skies are kind of hard to find out there. I'd suggest checking a lunar calendar and trying to be in the Northernmost part of Cali on the optimal night. Ideally some place with elevation.
It's nearly impossible to find "good" dark sky on the east coast. From NYC (where I am) it's a 5 hour drive to either Cherry Spring, PA or 4 hour drive to Adirondacks, NY, both of which offer OK-ish dark skies.
Yeah, I'm kind of a night sky enthusiast, myself. Those maps don't really work so well in practice. They're a good starting point, but it's all very hard to predict. Light pollution is certainly part of it, but haze and reflected sun/moonlight are both big factors, too. Plus, in my experience the gaps you find in those maps are still kind of polluted. Don't get me wrong, if you find some elevation in Nor-Cal you're likely to find a much better sky than you would out East. Absolutely worth it, but it will take a little effort, and the Gods might spoil your plan.
Oh, and unrelated tip. If you haven't been there before, the Pacific is fucking cold. It's not like the Atlantic. I've been there in early Summer before and seen people wearing heavy coats out on the piers. SF is famously chilly. LA is perfectly pleasant until you get to the beaches. Then you've got cold air blowing in.