Spectators are allowed to enter MK and line up down Main Street, as well as the area in front of Cinderella Castle. This is because all runners must be completed that portion of the course prior to MK normal opening hours - so no admission is needed. Other parks will require admission if you want to see runners inside the parks. My advice is watch the start, then monorail to MK. You can see runner come down MS and then through the castle. After that, If you time it right, you may be able to make it to Polynesian and catch them along Floridian Way. From there, you're probably best just returning to Epcot and either entering the park to catch them coming around WS or just wait at the finish line. There are no longer viewing areas outside AK, due to the course changes. Best to stick with the official marathon busses, as they are given priority along any close routes and will get you there the fastest (of course, the monorail is also a great way). Uber/Lyft will get you stuck and sitting in traffic. Trying to catch runners inside AK will require park entry and will be cutting it close trying to get there from MK. There is no spectator area outside the park, as the course was modified in 2020 to include Blizzard Beach. You can also view runners as they exit DHS or anywhere along the Boardwalk or Y&BC Resorts, but will be unable to make it to the finish line in time from there. One possible factor I am not sure about is using the Skyliner. Not sure how or if that could work for marathon spectating.