If you want to go over to the GF to explore, walk from the CR to the MK and then head over to near the resort monorail upramp. No, you're not getting on the monorail; that'd be a little weird when you can do that inside the Tower, wouldn't it?
No, you're looking for the MK2GF2Poly boat dock. It's a breezy, relaxing ride to the GF and on to the Poly.
Or, if in the mood to keep walking, look for the new walkway to the GF that starts to the right of the boat dock. Security at the dock will gladly point it out as it's not easy to spot.
You can also walk on from the GF to the Poly if so inclined, although I can certainly understand reluctance in August heat. Maybe come back in fall or spring sometime, because it's a lovely stroll from MK to GF to Poly.
ETA: In case you've not ridden the resort loop monorail much, I suggest the walk because you get on the monorail at the CR and stop at the TTC, Poly and then GF. It can actually be faster to walk over to the GF as suggested at busy times of year.