I have a GPS in my Cherokee. Fortunately, I don't have to travel to dodgy neighborhoods much anymore, except when I go back home to visit my parents. But what I do is wedge the GPS between the dash and the windshield - Not the most secure location crash-wise, but it doesn't leave suction cup rings. One of these days I'll get around to fabbing up a quick-release mount.
As for the fast lane/slow lane, the law here in Jersey is essentially "All traffic must keep right except to pass, unless it is a 3 or more lane highway, in which case the second-rightmost lane is acceptable." I suspect it's the same most other places, but you can't legislate common sense or common courtesy.