We got our requests both times we faxed them. The first time at CR N Garden Wing, I requested a ground floor room close to the playground, and we got exactly that. We were about as far as we could get from the main building/food court, but I didn't ask to be close to it. Last month, within 2 hours of faxing my request, the room assigner from CBR called me because part of my fax was unreadable and she wanted to confirm what I was asking for. I got N Trinidad, she assigned it while on the phone with me. I had requested close to food court/pool and not too far from a bus stop, but asked that they pick the best location for me since they knew the resort and I'd never been there.
I don't know how much it helps, but if you will be there for any special occasions, mention it in the fax. Our first trip just happened to be during our 10 yr anniversary, and this last trip was within 2 weeks of both children's birthdays and I mentioned it was a birthday trip.
Happy Planning!