Since no one has yet given a more knowledgeable answer, I will just volunteer from my own visits to that beautiful island. On several short vacations to the San Juan area, we visited the main sights and had typical tourist contacts. read more
According to a 2009 study by the University of Puerto Rico, nine of every ten Puerto Ricans residing in Puerto Rico do not speak English at an advanced level. More recently, according to the 2005–2009 Population and Housing Narrative Profile for Puerto Rico, among people at least five years old living in Puerto Rico in 2005–2009, 95 percent spoke a language other than English at home. read more
It is safe to say that many people speak/understand english, and that rate will grow (the Puerto Rico you see now is a very different Puerto Rico from 60 years ago) Their fluency rate may vary (people from San Juan may often speak better english than, say, people from Jayuya, for example). read more