Puerto Rico is a self-governing commonwealth in association with the United States. The head of the Commonwealth is the US President. Spanish is the main language of the executive branch of Puerto Rican government, but the official ones are both Spanish and English, as the government of the Commonwealth has to keep in touch with the American one. Spanish is just more commonly used. It's the only official language of the judiciary system of the commonwealth. All official business of the U.S. District Court for the District of Puerto Rico is conducted in English. Only a few people in Puerto Rico speak English, only about 10%. 95% of the population know Spanish. In general, the culture of Puerto Rico is a colorful mixture of different nations. Emigrants from Spain, Cuba and the Dominican Republic brought their traditions here, creating the unique atmosphere of the island. A lot of tourists come here every year to enjoy this place and its hospitalable and original people.

More Info: en.wikipedia.org