Not on the coast, but if you cut over to I-5, weather can be pretty brutal North of Redding/Red Bluff on up to and past Grants Pass in OR
I did not see the 3 day thing, sorry. I would second taking Hwy 1 North of SLO on up to San Francisco, very scenic. The Columbia River Gorge West of Portland is pretty cool, but you are sort of like Bandit and the Snowman, you got a long way to go, and a short time to get there.
Hearst's Castle is pretty awesome, but you won't really have time.
Here is what you would be missing
Hearst Castle