Thanks everyone. I have timed the walk from all 3 resorts.
HRH - 5 minutes to USF. You'll be spoiled.
RPR - 7 minutes to IOA.
PBH - 13 minutes to USF. It's 8 minutes from the boat dock of the PBH to the boat dock of the HRH. Then another 5 minutes to USF.
This was walking at a normal pace.
With the HRH you can walk back and forth many times during the day. It's like the hotel is connected to the park.
At the RPR it's slightly farther.
For the PBH you can walk it, but it's best to take the boat back after your feet are tired.