Go south. When coming down the coast, I have found myselft climbing at 28mph because of the tailwind. I can hardly imagine having to go the other direction.
In the book "Bicycling the Pacific Coast" by Kirkendall and Spring, the preface is entitled, "Why North to South?" Here's some of it, telling about Kirkendal's first coast ride, going north. (I think copyrights allow this since I'm giving credit to the book and it may increase sales of the book. If the owners of the copyright don't like it, I'll edit this and remove the quote.)
"North of Santa Barbara, encoutered stiff headwinds that blew the fun right out of his adventure. Scenery and the thrill of exploring became secondary to his daily battle with the wind. The wind created an invisible, never-ending hill that had to be constantly climbed. The wind beat dirt into his face, produced an annoying whistling through the vents in his helmet, while attempting to push him back to Mexico. By San Francisco, riding had become a chore. In Oregon, 80-mile-per-hour winds blew him to a stop while going down a steep hill.
"When describing that trip, Tom will pull out his trip journal. The beginning of the journal is full of his thoughts and impressions; in the second half he wrote only of the wind. His journal describes how he got up early in the morning to avoid the winds that blew strongest in the afternoon. ...Nowhere in the second half of that book is there any mention of beautiful vista points, magnificent redwood forests, sea otters, sea lions, lighthouses, sand dunes, and fascinating old forts. Nowhere is there any mention of the word fun.
"The following summer, Tom and I rode back down the coast to prove it can be fun. It was an incredible trip. The wind was still blowing but this time it was pushing us south. Near the Sea Lion Caves in Oregon, I had to apply my brakes to stop on a steep uphill grade....We were surprised to note that the highway department expects cyclists to travel from north to south. We frequently enjoyed a good shoulder on the southbound side while northbound cyclists had to dodge trucks and cars on a shoulderless roadway."
