I tried to get into Casa Ybel on Sanibel Island, Florida. They told me that there is absolutely nothing available in 2010.
It's getting very (very!) late for a 2010 exchange anywhere, let alone Sanibel Island---as bwvBound notes, that's a very high-demand area nearly any time of year. What's more, calling periodically will not be as useful as placing an ongoing search for what you want---and some do speculate that this
is something that is different between II and RCI.
The best way to improve your chances of success in RCI is to plan farther in advance, and place an ongoing search being as flexible as possible about destinations, dates, or both.
As for renting from the resort vs. exchanging---just as with
DVC, most resorts own some of their inventory directly; foreclosed intervals, deedbacks, that sort of thing. Those resorts have a duty to their other owners to try to get as much revenue for those intervals as they can, and that means renting them out for cash rather than depositing them to an exchange pool. Some resorts also manage rental pools for their owners who which to monetize their time rather than exchange it---one of mine does this.
Finally, if I were in your shoes, I'd simply rent out my points (perhaps using David's "broker" service) and use the proceeds to rent the unit on Sanibel that I wanted. I bet you'll have money left over.