I find Spanish spoken in Puerto Rico to be very interesting to analyze and study. Without a doubt it definitely fits into the mosaic of Spanish spoken in the region (referring to the DR and Cuba) It has many lexical similarities to the Dominican Republic as well some regions of PR have close similarity to accents of the DR. What gives Puerto Ricans away are their own regional variations in pronunciation, intonation (which is vey distinct in my opinion) and the overkill on the /r/ to /l/ change. Although this linguistic characteristic is heard in the DR as well, in PR it's much more predominant.
With reference to what I stated above some Puerto Ricans can be difficult to understand and the differences range from the larger city speakers i.e. San Juan, Santurce, Bayam?n etc to people from the campo that exhibit all the typical anomalies of Caribbean Spanish. I also find that Puerto Ricans in the USA speak quite differently from those on the island. I saw an interview of Daddy Yankee on CNN en Espa?ol recently and I was quite intrigued by his speech. Although he speaks like a typical Puerto Rican accent and vocabulary wise and with other noted peculiarities his speech was quite free of the 'typical barrio Spanish' which most people associate with reguetoneros. His accent is absoultely classic and a PR accent that I like.
-MP.