Depends on which way you go - much more to see if you take the 101/Coast route than the 5 - unless you're a country music fan and want to go to Bakersfield!
The 101 is about twice as long time-wise, but beautiful - Big Sur, Monterey ( 17 mile drive really gorgeous - plus the aquarium is great), Carmel, Solvang, Santa Barbara, Redwoods. So for a 2 day trip I'd definitely do that. San Luis Obispo area is probably about 1/2 way and has some nice wineries - along with the Madonna Inn. I've never stayed but it's pretty famous ( and pretty pink ) - rooms have themes, like the "cave room" ( all on their website)