OK, this is my experience. We did not know it was a Marathon Weekend. Depending on where the marathon is will determine if there will be a delay. Buses were never a problem at CSR, but this one day was horrible. We had planned to go to MK. We saw 1 bus for Epcot, about 5 for DHS, and 5 for AK. We asked one driver about a bus to MK and he said it was right behind him and he was correct. The problem is the bus driver didn't tell us it was a 1 hour ride to TTC because they could not go to MK. Then at the TTC it was almost another 2 hours to get a monorail, ferry, or boat to MK. Yes, it was a nightmare and the single worst experience of buses we ever had.
We did complain at Guest Services at DHS when we took a cab from the Poly to get there instead of going to MK. They were very apologetic. They also suggested we take to Guest Services at the resort because they were supposed to have signs up and notify guests of the delays the next day because of the marathon. In the end, we were given 8 FPs for each person (4 for MK and 4 for Epcot) in our group on our next visit. It was more than I expected and I didn't expect anything. At CSR, Guest Services stated someone was supposed to be at each bus stop and a sandwich board stating the marathon. It said to avoid MK and Epcot until after 12PM. They did acknowledge that they were not there because they got many complaints.
My advice is to do your homework for that day and avoid any park that could be impacted by it.
