I would honestly recommend Dorado (again). Dorado has English speakers, but not overflowing, although it will be hard to find a place overflowing with Angloparlants, unless it's touristy, which Dorado technically is...
Just go to Dorado My recommendation
There are many areas of PR that have concentrations of bilingual schools (Dorado is one of them) and in these areas you will find Puerto Ricans and the youth speaking English.
I had a Canadian friend who came down here to live though and he learned Spanish perfectly with the same Boricua accent.
You could also try the West coast, other forumers can go more into detail about that region.
And finally, there is Ponce. It is a really beautiful city in the same league as San Juan, but it's like a hidden secret and is not overloaded with tourists.