For the half marathon, you won't see much of anything at the start at Epcot, so position yourself in MK on Main Street. She will come in near Tony's, head up Main Street, veer off to the right at the Tomorrowland bridge (you won't be able to go past Main Street) and then come through the castle from the back to the front. She'll leave MK and head back over to Epcot, do a little loop in Future World and then finish in the parking lot (over to the left- facing Spaceship Earth) that is closest to Caribbean Beach Report. You can hop the monorail from Epcot to MK and then hop it back to Epcot. It will be roughly 6 miles over and 6 miles back, all of it adding up ot 13.1 miles. The race starts at 6AM, so you need to be at Epcot early to catch the monorail and not get caught in traffic.
They do have bus transportation to and from WWoS for the Expo and dinner.
We were staying at OKW and I dropped my husband and his friend off on Bonnet Creek Parkway (at the corner of OKW where the traffic light is closest to Port Orleans) and they walked to the full marathon start. My friend and I continued over to Epcot, had to go the long way since the road is blocked off (towards CBR, Disney Studios, BW, etc). I think we arrived at Epcot about 5:15 or so. I think we left OKW about 4:45AM. It was slow getting into park, but not horrid.
We rode the monorail over to MK, watched the guys run down Main Street and through the castle. Then we hopped the monorail back to Epcot and got the car to drive to AK so we could see them come out of AK. Then we drove back to Epcot and waited in the parking lot for their finish.
The two guys did the Goofy Challenge that year. But I did the 5K (that was the last year that it followed the half marathon at Epcot), so we didn't follow them to MK for the half.