It kind of depends on your luck. If you get there right when an Epcot bus pulls up, vs. having to wait 20 mins for one makes a big difference. The number of stops the bus has to make (It takes at least 5 mins to go to all of the POR stops, then longer if you stop at FQ too). So, sometimes you get a nice short ride, but 30 mins isn't unheard of.