Don't be scared away from this drive. It is absolutely wonderful.
(any others familiar with this route, please feel free to jump in)
The coastal route is not to be missed. However, after you get half way through Mendocino, RTE1 Jogs over to 101,m so you don't have to worry about choosing which HWY after that. It's 101. You can drive to the coast off the 101 and back again after RTE1 turns into 101 though if you want to see something on the coast.
Of course RTE 1 is definitely one of the most beautiful drives along a coastal area in the world. If you start in Santa Monica, take it all the way up. Fabulous indeed. It gets better and better as you move out of the Southern part of the state into the middle and norther part also, simply because of the cliffs and rock formations.
If you remeber, call me when you get to Humboldt, and I'll take you to the top of the Trinidad head, something missed by most people visiting. If it's a clear day, you can see 20 miles each direction. Another look out spot is called Strawbery Rock, which isn't on any information pamphlet because it's private logging company land, closed to teh public. However, with all of the activists in this area, the company doesn't keep people off the trail leading up to the rock. Once there, you can see the entire coastal range of redwoods and if clear, perhaps 50 miles each direction. It's like flying in a plane. If the clouds are right you could get an image that is a show stopper. Very hit and miss in this area though. I think this entire year I may have seen 5 good sunsets so far. The beaches have so much rock formations that if the clouds participate and the light is good, you can't help get a good image.
I think two years ago I shot the Trinidad coast everyday for a solid 60 days and only got a few keepers. This is one, and you can still see that the clouds are not the greatest and you can see the haze in the air too. I just tried to frame it compositionally so that the clouds were not the subject, but the rocks which were the result of a -6 low tide--which doesn't happen too often. Taken with my 5D: