There is Hwy 1 (Pacific Coast Highway aka:PCH) and Hwy 101, in some places they are one and the same, but mostly PCH sticks close to the coast and is at most 2 lanes in each direction. The 101 is mostly 2 lanes in each direction and is freeway or limited access highway. The 101 goes inland from the coast and is heavily traveled. Staying right on the coast you may see some frost in the early mornings but usually not more than that (mostly due to the ocean warmth). Inland on the 101 will see colder temps but besides some frost but agian it not that bad. Further north from SF you go it will get colder. Last January I rode up to Washington from Southern Calif. Way North of SF I went up Interstate 5 and got into real cold temps (mid 20's) and some freezing rain. Again way North of SF I came back south on PCH and it was low to mid 30's in the mornings, but by noon it was in the 50's.
"I couldn't wait for success, so I went ahead without it."