If you're going all the way to SAC, there is an amazing burger place across the street from Sac City College, called Burgess Brothers. It's a couple of miles, maybe a bit far to walk.
Props is at WVI, but it's a burger place. It's OK, but you might as well just go to 99 Bottles if you live in Santa Cruz. Same management, different menu, but similar quality. Not bad, not great.
The old Nut Tree is now a big strip mall, but it has Fenton's if you're into that. The ice cream is a lot better than the food. Once again, if from Santa Cruz, Marianne's is better.
I didn't find the food at Columbia to be all that good, but the town is quite interesting. It's a well preserved gold rush town in the Mother Lode. If you're going that far afield, perhaps Harris Ranch (3o8) might make more sense. Rumored to be the best steaks in California, with an airstrip right alongside. But it's halfway to LA. Like a lot of Californians, I've driven by there hundreds of times with the windows rolled up, but never stopped.
There are a few decent restaurants in Booneville. It's about a mile walk to town.