Wildnfree
This is a very open ended question. Therefore expect a range of answers. Although these two islands have plenty of cultural similarities of course there are differences and it depends on what you are looking for from a cultural and social point of view.
I was lucky to have the opportunity to study in San Juan and I have nothing but positive comments about Puerto Rico in general. Of course my time there is not sufficient to make a final assessment but I would go back given the opportunity.
Your statement about Puerto Ricans refusing to speak to one in Spanish 'if you are not Puerto Rican' sounds like one of those infamous over generalizations that people make about nationalities. I have never heard that and my point to you is if you are planning to be outside of the tourists areas of San Juan for example el Condado - si no hablas español vas a sufrir. If you go to other parts of San Juan (non tourist areas) and especially other parts of the island like Ponce, Mayagüez and Cabo Rojo I suggest you know how to speak Spanish. Do some research on
www.puertorico.com and many other good websites.
LDG.