In our experience.
Unless you are staying in 4* or 5 * accommodation or it is otherwise stated the pools will be unheated and freezing.
If they are climatized as they call it , some of the pools are O'K to swim in.
Again it depends where you are staying.
But in 15 years we have never found a warm outside pool.
Apart from the one pool at The Cordial playa Hotel in Mogan, that was warmish and fine to swim in.
But I'm sure someone will tell you different.

When we stayed at the Riu Clubhotel Gran Canaria last February, the brochure claimed the pool was heated, but it was indeed freezing! I would recommend you email any hotel in which you are interested and ask what temperature their pool is heated to, to be on the safe side.

In all the times i have been to Puerto Rico i have never found a heated pool ( i always go in winter) except the public Lido, which is lovely.