If you go to the TUG Resorts and Reviews, linked in the red bar at the top of the page, you can view each region/island, see how timeshares are ranked by Tuggers, and which exchange company they are affiliated with.
Of the 3 regions you are asking about, Carmel/Monterey has the least availability, so you may want to start there, and build around that reservation. Getting 3 reservations that match exactly will be challenging, so you will want to be flexible, and be prepared to link exchanges with 1-3 night hotel stays, if necessary.