Update:
I went up to the areas around Marysville and Washington last weekend with a few friends and two dogs. The public ground was the most desolate thing I have seen in a while--and I've spent a fair amount of time in the Nebraska sandhills. West of Washington, however, the opportunities looked better, though we never really found too much on public ground (just a few hens, no quail). We did knock on a few doors and found the land owners to be quite accommodating.
The first house we knocked on let us right into a chunk of land that we were drooling over when we were cruising for spots. They said "you ain't gonna find nothing, but have at it boys" and luckily for us, they were wrong. We scared up a massive covey of quail within the first 50 yards of walking and in their field across the road we kicked up 5 roosters. Not phenomenal for 100 acres, but not at all bad.
The second house we knocked on had approximately the same amount of land (all thick CRP surrounded by milo, with a few small water draws) but after scouring the whole plot we only kicked up one rooster. So our trip wasn't a total loss, but for how much we walked for those few birds I wish we would have seen more. Oh well--there's still two weekends left to hunt. Next weekend may be a trip out the land by Ft. Hays.