If you usually stay at a monorail resort, I would encourage one of those resort choices if you intend to do MK or Epcot on Saturday or Sunday. In the morning before the runners for the 1/2 and full clear the roads it's pretty impossible to get anywhere near MK taking a bus. Before I knew all about Run Disney events, we were at Disney during marathon weekend and were trying to get to MK the morning of the 1/2. We sat on that darn bus for an hour and a half. At least we had the park practically to ourselves when we finally made it... If you aren't early risers though, then this may not be as big of an issue.
The work around for this blockage is to take a bus to Epcot (either regular Disney or Marathon) then monorail up to MK. BUT you have to know about the likelihood of traffic from the events. Disney usually does a great job of notifying guest of traffic issues that may arise from the events but not everyone reads the letter or understands.
I was wondering this myself....as I have started my C25K program.....I am hoping to do the Family 5K during marathon weekend. I was looking at The Boardwalk - but I just don't think I can afford it.
I see you have to bus to the start and the expo anyways, is there a benefit to staying at CBR say vs. Port Orleans?
I do not think you will have any issues with race transportation. The marathon buses run regularly and on race mornings field level dispatchers are manning the stops in the event of snafus. At either location look around on Thursday afternoon at the marathon bus patterns. As an example, at CBR the marathon busing will enter and exit through the Victory Drive entrance, not the main entrance (or did a few years back when we stayed there annually for the marathon). That means the first island picked up was Jamaica. It will give you an idea on if your stop is going to have a few drive bys (ie. the last o the loop) on race morning, or at least where you may need to walk to see the bus first.
I have a question about your phrase…” I see you have to bus to the start and the expo anyways”… Note that for the January races buses run from every resort to both the expo and race starts. This busing is not the regular Disney property busing, rather charter type buses with Marathon or Expo in the window. Depending on the resort, you may or may not have a special bus stop. For instance, the marathon buses stop at the convention center at the Boardwalk and Yacht Resorts, not at the regular bus stop. At CBR they historically stop at all stops and at OKW only some of the stops. Confusing but easy to spot once you arrive. Note that you do not have to ride a bus, you can drive if wanted. The buses are convenient and save on mental wear and tear but frankly I have driven to the race as many times as I have taken the bus; and even drive a higher percentage of time to the expo.
Just a word of advice, do not ask a cast member questions about bus transportation before Thursday morning, and even then you may want to confirm through several independent members. Disney is a great planning organization but they do not let the line folks know about upcoming changes until they actually need to know. I have held a Q&A session a few times in the check in area for the Boardwalk and CBR when I over hear a weekend question and see that the CM does not have the answer. It morphs from me asking if I can butt in to someone else having a similar question and then we tend to draw a crowd. The best piece of advice I can offer on race weekend is go with the flow and leave early just in case the flow was not right.
[ADDED] - OK Really final. The Pop makes a great marathon weekend resort, also; or at least until they open up the new section across the lake. It has one bus stop, shares nothing transportation wise and as an added bonus.... you are at the resort where the WISH folks meet for a pre-race meal!