San Luis Obispo is pretty much slap bang in the middle between SF and LA, and is my usual stopping point. Madonna inn is fun, but also plenty of motels there if you prefer.

There are some great vineyards in the area - totally different wines to napa, and (dare I say it), not as pretentious as some of the napa places. I highly recommend the tasting room at Tangent winery - I discovered their superb albarino on an F sector a couple of years ago and made sure to visit next time I was in the area and it did not disappoint.

Its less than a 10 min drive from there to shell beach, where you can stop by Zorro's for some food (superb place & food despite the name), and when you have finished there you are right by the 101/1 to head south again.