We just stayed at POR in February and have been there other times as well. This time we booked a preferred room (extra cost - but not too much at the time we went anyway.) This guarantees a room close to the main buildings - which for us anyway - ended up being AB. I would imagine they would primarily consider the AB side to be preferred as the walk to the main buildings is decent from even the closest room on the Mansions side. I was hoping by booking preferred location we'd get AB because with a teenage daughter who does not want to sleep with her younger brother - the trundle is fantastic! Sure enough that's just what we got even though we didn't check in until after 8 p.m. we still got an AB room. So, I'd think about booking preferred and noting AB on your request for an even better chance.