bikingshearer 

Someone asked this same question a few years back and got some useful responses. Try the search function to see if you can dredge it up. (This is meant to be helpful, not snarky.)

I have limited experience, but I'll pass on my thoughts.

1) To the extent that the logging industry is still going, watch out for logging trucks. They go like the proverbial bats out of hell. Not surprising, since they are mostly paid by the run.

2) Do not under any circumstances go on anything that is not a paved road, or at least a significant dirt road. Pot is still the biggest cash crop in the area and there are still way too many illicit pot farms in the backcountry (and not-so-backcountry) over which the entrepreneurs are, shall we say, extremely proprietary. I'm not a mountain biker, but I would think this would put a serious crimp on the style of any single-track fans.

3) Not a ton of paved roads compared to the Bay Area, but what is there offers stunning scenery. It can also offer the aforementioned logging trucks, tourist traffic, or both.

4) The drivers on the whole are not nasty, but can be blissfully unaware. Winnebagoes especially fit this category. The truckers have gotten better over the years, but the winds they create can still be scary as hell on the narrow roads.

5) Arcata is a pretty hip college town, so my guess is that the cycling cultue scene is best there.

6) The economy is not been kind to the North Coast for many years now (a big reason why marijuana is such a big cash crop). Significant portions of all of the towns can be surprisingly seedy as a result. Not Skid Row seedy, but definity down-at-the-heel seedy. Silicon Valley this ain't.

7) I hope you don't mind fog and drizzle.