I have to say, that while I loved the Casitas (and didn't have any problem with too many conventioneers), I believe I would have been happy in any of the sections. My preference was the Casitas as I think they are beautiful then the cabanas, as I had stayed in the Ranchos on a previous trip (and had no problem with them).
I plan on requesting the cabanas next time as I want to try all 3 sections.
You'll be happy no matter what building you stay in. The resort is beautiful, romantic, and relaxing. Think about what you want, make requests, but don't worry.
My one big suggestion which you probably already addressed: if you want a king room, request. We decided to save money and go with a standard room. By the time we went, we had a little extra money and asked if we could get a king room (we were willing to pay). They tried but there was one night during our stay that it wasn't available so we ended up with what we reserved.
Our standard room view was, luckily, not of the parking lot, but of a grassy area with trees and a turn around. Not a perfect view but it didn't bother us at all.