Personally if I wanted somethig special for a birthday I'd order something from Disney Florist. I think for as many people that get something in their room, there are just as many who do not. Just depends on the CM at the time. From reading these boards over the years, it seems to be pretty hit and miss.
Still mention it, but this way if you do find something special in the room, it'll just be a bit more magical.
JMHO
Cyn