Not really any help with preferred rooms, but when we went last year, I specifically requested 80's (non preferred) close to transportation and we were the the second room from the North Rubicks cube and just had to walk maybe 85 yards across the parking lot to the buses. Felt like a preferred location but didn't have to pay like it was one.
My one stay at the Pop was in 50s building #1. I walked right up the first staircase, and was on the right side, facing a lot of greenery. It was a great location, close to everything, but very quiet.