Are you sure that you need one AP per hotel room? In most cases 1:3 (the room itself, one on the back side of the AP and the room at the opposite side of the AP) provides adequate coverage. I can imagine that mounting the AP's back to back can cause interference, but honestly is dependent on the attenuation of the wall. Quite likely, if you have high attenuation in the walls, that may be a reason that you might require one AP per room, in that case you will be fine as the wall provides enough separation.
Please seek advice at a local HPE Aruba partner, as this is not as simple to answer as it seems.
Please do a validation on site (site survey) for ate least a few rooms, so you know the radio (RF) characteristics of the building.