I would say that from San Francisco to Santa Cruz is amazing on the 1. Same goes for San Francisco to say Fort Bragg on the 1 (amazing scenery).
If I had only two days, I would recommend San Francisco to Fort Bragg, cut across the one north of Fort Bragg to Garberville (7hours) from there you have the Avenue of the giants scenic detour. Its about 20 - 30 miles to the end of this route north of Garberville. Lots of Redwoods(the biggest in the world). The road back to S.F. on the 101 is about 4.5 hours.