I finally decided to cross Mendocino National Forest off my list. It's amazing that it's so close (3.5 hrs) and yet so few people have been there, or even heard of it. I went to Snow Mountain Wilderness and headed up to the summit. With the Central Valley roasting at about 103 F, it felt about 85 F at the top. There were still some very small patches of snow.
The environment seemed kind of like the Sierra foothills, but even drier, with a lot of the coastal scrub you'll see on the east side of slopes in coastal Marin. Highlight: Summit Spring, which had the highest flow of any spring I've ever seen. Not much wildlife, except the bumblebees were curiously interested in me, more like horseflies, and there were lizards everywhere - which makes me wonder how they survive 5-6 months covered in snow up there. There was an odd crow conference going on over the summit - I saw very few but there were making a big, gregarious circuit over the top. In the heat it was too hazy to see the ocean.
On the way back I went out of my way to check out Black Butte Lake. I've always wanted to see this lake. Ever notice that weird sloping mesa to the west as you drive up I-5, around the exit for Orland? That's Black Butte. The lake was surprisingly warm (lots of people swimming) but not that clear.
Overall, Mendocino it seemed more popular with the offroad vehicle crowd than hikers, but still only saw 4 of either. If you want isolation you can get it there, and I'm glad I checked out this N.F. but wouldn't go out of my way to visit it again.