Posting my response from the resort boards, in case it's helpful to other runners!
We just ran the 5K, half marathon and marathon last month and stayed at Poly. We love Poly in the first place, but the primary reason we selected it for marathon weekend was how amazingly easy it was for spectating the races. I ran the 5K and full marathon and spectated the half. My husband and teens ran the half and spectated the full.
The morning of the half marathon, I did the following:
1) Walked to the TTC (less than 10 min walk) to see our runners;
2) Walked back to our room to deposit the extra clothing they gave us and grab some breakfast to go from the Poly club lounge;
3) Walked to the front entrance of Poly (less than 10 min walk) to see our runners again - signage was great and CMs directed the way;
4) Walked back to TTC and took monorail to Epcot;
5) Saw our runners at the end of the monorail ramp, as they entered Epcot;
6) Walked over to the finish line and saw our runners right before they crossed.
That's four different spots and I was leading my parents and our 8-year-old along the way. It would have been much easier with a tiny one in a stroller, at least in my opinion (our 8-year-old does not walk quickly and he's too big to carry!)
The morning of the marathon, my family did the same at Poly - walked over to TTC to see me, then front of Poly, then they hopped on a bus to WWOS and then met me at the finish.
I should add that we've also stayed at GF and CR and enjoy both of those resorts. For half marathon viewing, CR guests can see their runners once from the front of CR, board the resort the monorail to TTC, then transfer to the Epcot monorail to the finish. GF guests can see their runners once from the front of GF, take the resort monorail to TTC, then transfer to the Epcot monorail to the finish. The advantage of Poly is TWO viewing spots within walking distance (Poly entrance and TTC), and then the direct monorail from TTC to the finish.