My DD was sick during our 1st Poly stay in 2010. I asked the lobby concierge if they had a DVD player we could borrow. They were able to have maintenance come and install one.
The non CL rooms are not equipt with DVD players, so I am not sure if we just got really lucky or they keep a couple around.
You can buy a Blu Ray player for less that $30. I've seen new standard DVD players for $15. Usually they take up about as much room as a couple of books. If it's important, I wouldn't leave it up to chance.
Club level rooms have them, otherwise I think you'll have to bring one from home to guarantee you'll have it. I have a small one I pack when we travel along with an HDMI cord. It's very easy to plug in to the tv, and we like having it.