There are three public lines...at MK there is the express line...stops at TTC and MK only. It runs counterclockwise. The resort line, runs clockwise...TTC, Polynesian, GF, MK, Contemporary, back to TTC. There is the line that runs from TTC to Epcot and back again.
If you ride the Epcot line back to TTC and want to hop on the resort line, you are going to have to get off when you get to TTC, then walk down and back up again to the Resort Line...not a huge deal, but I like to be sure people know they just don't get off one, and then walk 3' and hop on the other line.