It very much depends on the thickness and the material that the walls are made of (and the power of the signal that you intend to transmit from the access point).
I have successfully connected a PC to an access point through two fairly thick walls which I think were built from breeze-blocks, with a plaster finish. The signal strength/quality received at the PC did vary in different parts of the room though.
Unless you can do a wireless survey, it will be a case of "suck-it-and-see" I'm afraid.
Pete