I believe you meant to say "Rural" area drivers are most courteous, out in the country side this is the norm. If you are in or near any mid - large size city that all changes. I have also witnessed this odd but appropriate behavior in New Mexico and Arizona, but as stated above, you must be away from any city.
I have seen the signs as I am originally from Austin, it does help, a little. What they really need is for the Hwy Patrols to start enforcing this with stiff fines, then we'll make some progress. If the Patrol can harass the speeders for speeding, they can harass the slow pokes who park in the passing lanes and can't comprehend what they read on the posted signs.