Like Fran, we've had some 'interesting' bus rides, mosly in the hinterland of Mexico.
Mexican buses stop in the back of beyond, have no facilities, are prone to breaking down, but have some very eclectic travelling companions and travel through places and scenery you would never see on a plane or via the sanitised tourist route.
We always try to 'go local' when in a foreign land and never act like typical Brit tourists that stand out a mile - works for us.