Sacramento is the confluence of four very large freeways: the 5, 50, 80 and 99, thus it's very easy to get to a whole lot of people with a minimal amount of driving.
I like putting small signs on large overpasses. Although they're perfectly readable, those who'd be inclined to take them down are far less likely to do so.
Fencing in front of bushes makes for a perfect posting blind. This sign required about five steps from the parking lot, but is entirely invisible.