I've ridden the route through Lompoc and onto Santa Barbara via Highway 1 and then 101 several times.
I prefer Harris Grade Road into Lompoc and, as you will see from all the writing on the road, so does everyone else. The miles from Lompoc to 101, what hueyhoolihan called the "seven mile grade" is one of my favorite rides south of SLO. It is a steady but mostly mild uphill on a wide shoulder through ranching country criss-crossed with creeks. The 2 mile straight down to 101 is a rush on a loaded touring bike!
I'd stay off 101 for as long as possible. It is a freeway with lots of cars and trucks and isn't pleasant to ride on.
The part of 101 that you do have to ride on, through the Gaviota Pass and then down to the Hollister Rd exit is neither fun nor pleasant.
Be aware that there is a bike/walking path that connects Gaviota and Refugio Beaches, though it is often closed for (no) repair. To get on it, you exit just past the rest stop in Gaviota Pass toward the State Park. It will get you off 101 for a couple miles.
The road from Carpinteria to Ventura, along 101, is not something for the faint of heart. For some of it, you are riding on local or frontage roads. But, for about several miles, you have to ride on 101 itself and the bike lane is right next to traffic. It is harrowing bike riding and I have only ridden it once. The first time I rode down to LA. Ever since, I have gotten friends who live in Santa Barbara to drive me down to Ventura and started riding from there. I don't know what the route that bypasses 101 is like, but I'd take it to avoid the part on 101.
If you are interested, this journal page describes
the ride from Lompoc to Santa Barbara.
It is a great ride. Have a good time.
Ray