I've got the Washington County 'Country Cycling' map. With the exception of a few small complaints...a great map to have, though presently out of print. It shows parts of, as you refer to it, 'the hill country; an area between the points north to Hwy 26 and beyond...about 10 miles south of Hagg Lake...and 10 miles west into the hills. According to this map the hills are laced with roads, but they're all gravel with the exception of Hwy 26 and what I'm guessing might be the Wilson River Hwy (could be it starts out as Gales Creek Rd).
Suitably equipped, I'd love to go out and explore by bike, some of the country those roads pass through, but I'd be very careful before I did. The map doesn't show that there's anything even remotely like a village or even a store out there. I suppose some of the land is timber company owned, but who actually might live out there is something I wouldn't know about, and it certainly can't be determined by this pretty good map. People could ride up there, have a problem and have who knows how hard a time getting back out.
Who would a person contact to find out about route advisability out and up through the hills? Probably someone in the county offices. Maybe contact the Washington County Department of Land Use and Transportation Planning Division? It had a hand in creating this great map I have. Report back here. Most likely, other people would also like to know more about the situation related to routes up through the hills.