Puerto Rico is a wonderful place for North Americans to travel to because the English language is so widely spoken and understood there.  For those who either do not speak Spanish or who do not speak that language fluently, a few recommendations:

1) When speaking English to locals, it often helps to slow down just a bit and to speak clearly, particularly in areas that are less frequented by tourists.  Bear in mind that while Puerto Rico is legally a part of the United States, it is culturally part of the Spanish-speaking areas in and around the Caribbean.

 2) If you want to try out your Spanish, try as best you can to pronounce the words you utter clearly and correctly.  A slightly mispronounced word can cause a serious misunderstanding or even offense in some cases.

 3) Even if you know no Spanish at all, invest seven or eight bucks in a pocket Spanish-English dictionary before you go.  It will come in handy for reading signs on the highways, stores, etc., most of which are in Spanish only.

 4) Saying "gracias" (thank you) is good. Contrary to previous information, don't say "gracias señor" as this can be interpreted by most as "thank you, Lord" instead of "thank you, sir"

 5) In North America, they have one chunk of culture in common with people in Puerto Rico (and the Spanish-language areas in and around the Caribbean generally)--baseball.  Baseball is taken seriously in Puerto Rico; one of the island's national heroes is the late Hall of Fame outfielder for the Pittsburgh Pirates, Roberto Clemente.  Whether you are speaking English or Spanish, it is generally easy to strike up a conversation with a local about baseball.