Usually there is always good availability. You can book at 10 months out.
However, they are doing construction now - which may cause harder to book reservations. Prime Christmas/New Years is harder to book.
I recently stayed for a week at Gran Melia Golf Resort in Puerto Rico and drove over to the Wyndham Grand Rio Mar to view it for a potential future stay. Wyndham Grand Rio Mar has a nicer sandy beach with ocean waves.
I liked both, but I preferred my choice staying at Gran Melia. I booked with RCI doing an exchange with points. There are 2 Beautiful pools at Gran Melia. No water slide. The Gran Melia has a full kitchenette - no dishwasher. Free parking for Vacation Club exchange, Free Continental weekend breakfast, Free drinks including wine and beer in the club lounge. Free use of Bali Beds at the club pool.
Wyndham Grand Rio Mar may be better for a family once they have the family suites after construction. I liked the pool and beach very much.
We visited El Yunque Rainforest too. Rent a car if you go. There is so much to see in the area and having a rental car was a big plus.
Cynthia T.