For one of our stays at Pop Century, the room we had been assigned wasn't acceptable to us (it was smoking back when there was a difference). The room was a standard room and we had stayed in standard before. For the trouble, we were given a preferred room for free (I think preferred is $10/night more? but it does cost extra). We did NOT like the preferred room at all. I didn't t hink we were any closer to the food court or bus stops. It seemed louder because of the location. I'm glad we were given the preferred location, though. Made it easier in my mind that I don't have to request it in the future.
You should have your room requests noted on your reservation when you make it. If you've already made the reservation, call back and have the requests put on there. Put the requests in order of importance. If a first floor room is important, put that first. And remember that the more requests you make, the less likely you are to get your perfect room.
Rooms are usually assigned a few days before you get there. Faxing a request is not recommneded anymore but you can if you want.
And remember that no request is ever guaranteed unless for medical reasons or for connecting rooms with more children than adults in one room.