Hi....
Can't compare to Caribe Royal, but I doubt you'd get a "horrible" room. Some of the older sections may not seem as fresh or modern, but they are clean and nicely appointed. Most have had appliances all replaced so they should be brand new or near new. Do a search on these forums for pics of some of the older sections (there have been some recent threads).
Unfortunately, RCI exchanges are given lowest priority for room requests. Owners and renters tend to get first dibs. But it can't hurt to ask.
Fill out this online form :
https://www.svosecure.com/starwoodvo/diamond.jsp?resortID=5
Most people prefer the Lakes or Cascades (these are the two newest sections). After that, comes the Fountains II, then the Fountains I. Followed by Springs.
Most would consider the Courts, Falls, Spas and Palms the oldest and most undesirable, though these sections have all undergone rehabs in recent years.
Keep in mind, only the Lakes and Cascades buildings have elevators. The others are 2-3 floors high and would require steps. So if you have anyone with mobility issues or need to drag a stroller up and down steps every day, you might want to request "elevator or ground floor".
Please feel free to ask about any other questions you might have.