"Like any other state, there has to be compliance with this and any other federal law," Santorum said. "And that is that English has to be the principal language. There are other states with more than one language such as Hawaii but to be a state of the United States, English has to be the principal language."
Reuters goes on to report that neither the U.S. Constitution nor any federal law requires that a state speak English. Some states have established English as an official language anyway. To be charitable to Santorum, he did say that English should be the "principal" language, not something to be legally required. Puerto Ricans typically learn English in high school, but census data shows only about 30% of Puerto Ricans rate their ability to speak English "very well."
Santorum's presence in Puerto Rico may seem odd - governor Luis Fortuno has endorsed his rival Mitt Romney, and the candidate perceived as a moderate has won massive portions of the electorate in the past few years - John McCain, Bob Dole and George H.W. Bush all won massive majorities there.
The people of Puerto Rico go to the polls on Sunday to vote in their GOP primary. Puerto Rico awards a small number of delegates - twenty-three - but more than some small states like Delaware.