do you need to have passport to go to Puerto Rico?

yes

If you're visiting just Puerto Rico (not leaving for other carribian islands by ship/air) no passport is required, you can travel with driver's license/state ID just as you would travel between other states.

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For travel between Puerto Rico and the U.S., no passport is required, making it easier for travelers who don't have a passport and will not have to encounter long waits at customs and immigration. Puerto Rico, a commonwealth of the U.S. offers the best of a tropical island steeped in authentic Latin culture with the benefits of being a domestic destination, English is widely spoken and the currency is the U.S. dollar.

http://www.gotopuertorico.com/passport-information.php