Building 7 would be the closest.. but it is such a small resort, that being in building 7 isn't going to save you too much walking distance. I'd request 5, 6 or 7.... 5 to be close to everything at POFQ, and still not too far from POR. 1 and 2 would be furthest from POR.
We've taken the walk over before. it's a decent walk, but is a nice, pretty walk if you have some time. Maybe take you 10 minutes to walk it I'd say building 6 of POFQ to POR's pool. It's like walking 2/3rd of the way around the World Showcase at Epcot is my guesstimate when comparing to two distances on a map.
Maybe take a nice walk over... and then on way back take the boat back to POFQ. Could always take a bus over... others can correct me if I'm wrong.. but buses will pick up at POFQ and then head to POR to pick up too. can always ask the bus driver before getting on if he's planning on heading to POR.
oh, and yes, there is a path the follows alongside the river... is a very nice walk!