I believe their music sounds different, too. That's an easy way to get in trouble in Puerto Rico. Play music they don't like louder than they play theirs.
Well, maybe that's not so easy. Everybody can't afford speakers that big. ;^)
Oh, they can tell. I had the same questions about fifteen years ago, when I worked alongside two Puerto Rican girls who were constantly slamming Dominicans.
Their ethnic backgrounds are almost identical and they both speak Spanish. I don't understand this.
I moved to NY from Ohio, and I was truly puzzled by this. Gee, two Spanish-speaking islands in the Carribean, what's the diff? So I asked, and brother did they answer. They can tell the difference by accent, by appearance, by education level, by the living conditions they find acceptable, by everything. Including the names Dominicans give their children, which I am told are usually "made-up" names similar to some of the names inner-city black kids are saddled with here. They rattled off about a dozen "names" as examples and laughed until they were helpless (I don't speak a lot of Spanish so I didn't quite get the joke).
In other words, Puerto Ricans think Dominicans are irredeemable hicks.
There was a Colombian girl working there who told me that every other country in South America looked down on PR and DR and didn't see much difference between the two. But by then I had gathered that Colombians considered themselves "pure Spanish" and looked down on just about everybody else, so I took that with a grain of salt. What it really told me is that there definitely is a caste system of sorts down there, if unofficial.
WELL COMING FROM A PUERTO RICAN WHO KNOWS THE DIFFERANCE I CAN TELL YOU A COUPLE THINGS THAT MAKE US DIFFERENT. DOMINICANS TO BEGIN WITH SPEAK SPANISH VERY DIFFERENT THEY HAVE A STRANGE ACCENT THAT NO BODY UNDERSTANDS ACCEPT THEM. THEY ARE ALSO VERY UNEDUCATED AN POOR. THEY HAVE A CERTIN LOOK ALSO. JUST BECAUSE THEIR COUNTRY IS CLOSE BY DOESNT MEAN WE ARE THE SAME PEOPLE. OUR CULTURES ARE TOTALY DIFFERENT AND PUERTO RICANS ARE SO MORE UNIQUE THEN DOMINICANS WE BORIQUAS ARE US CITIZENS WITHOUT EVEN HAVING TO STEP INTO THE MAINLAND, AND ONCE WE DO WE SHOULDN'T FEEL LIKE FOREIGNERS.