I live in Mendocino County so I can give you about half the route. If your route takes you through Ukiah I would suggest heading out to Fort Bragg via either Orr Springs Road or Highway 253. Orr Springs is steeper but has less traffic, Highway 253 is longer and more heavily traveled. Either way you're going to have to do some climbing.
If you take Orr Springs Road you can follow the Comptche-Ukiah Road out to Highway 1 near Mendocino and then ride north on the 1 until you hit Fort Bragg. If you take Highway 253, you can pick up Highway 128 in Boonville and ride north to the 1 and north from there to Fort Bragg.
If your route from Sacramento takes you further south, you could take Highway 128 north and west from Cloverdale to the 1 to Fort Bragg.
In my experience, there aren't much in the way of logging trucks on any of these routes, but there is some traffic, more so on the weekends than at other times. Another thing to be aware of is that if you plan to do any renegade camping in Mendocino County is that there is a county-wide anti-camping ordinance. Given the size of the county and the size of the countywide law enforcement services your odds of avoiding hassle are pretty good, but it's something to keep in mind.
Anyway, that's my 2-cents.