Top do-not-miss sites along highway between San Francisco to Santa Barbara.

The can't-miss sights are (from north to south) Monterey, Big Sur, the Hearst Castle, Paso Robles (if you're into wine), Avila Beach, La Purisima Mission State Historic Park, Santa Ynez (again if you're into wine: even if you're not, the countryside at some of the wineries is beautiful) and Old Mission Santa Barbara.  La Super-Rica Taqueria in Santa Barbara is one of those places I'd fly 2500 miles just to eat at.

Carmel By the Sea/Monterey, Big Sur, Paso Robles (if you like wine), San Luis Obispo.

Also, check this out:

https://www.tripadvisor.com/Travel-g28926-c197885/California:United-States:Sf.To.La.Coastal.Road.Primer.html