Bedbugs have been reported at pretty much every WDW resort from time to time, and can happen even at a five-star hotel. It does not appear to be a widespread problem at WDW, not to mention POR, but it can happen. I remember newspaper stories from about a year ago that bedbugs seemed to be invading even the finest hotels in NYC since the tourist season had picked up.
It has never happened to me (trip coming up in Sept., so knock wood), or anyone I know. I suggest checking the beds before you unpack. If you do find bedbugs tell the resort guest services that you need to be moved to a different room and tell them why.
Bedbugs are caused by careless guests who bring the little hitchhikers in their suitcases, not by a lapse in the cleanliness standards of a hotel.