Every route I know has a large majority that is rural, even one with a fair sized in-town section. I personally didn't have a very hard time learning them. Just pay attention when they train you and ask a lot of questions about where different roads come out on and such.
I also make my own maps, and spend a lot of time on Bing maps just looking around for fun. It actually helps a lot. After a few runs of the route it all just comes together and I hardly even have to reference my maps, usually more often for the in town parts if at all actually.