We always have our car at WDW, and the two parks we drive to are AK and DHS. For Epcot and MK, we take the Disney bus. There are exceptions. If we're starting the day at DHS, then finishing at Epcot, we'll take the bus to DHS. If we're visiting MK and Epcot because one or the other has EMH, sometimes we might park at the TTC and monorail to both parks.
POR is probably our favorite resort. We've acquired the habit of leaving our room, heading to the food court, then taking the bus from the main bldg. That way, in case the bus fills up while making its 3 other stops around POR, we always have a place on the bus, and usually an actual seat.