[eridius]

It looks like approximately 1.8 million people voted on the first question, and 1.36 million people voted on the second. And in 2016 Puerto Rico was estimated as having a population of 3.4 million. In light of that, 1.8 million votes on the first and 1.36 million votes on the second seems fairly similar to the normal voter turnout in the U.S.

So no, it doesn't sound to me like a "small minority" of people were voting.

EDIT: This is talking about the 2012 referendum.

EDIT 2: It occurs to me that 3.4 million isn't the voting population, it's the total population. So the voter turnout is even better than it looks initially.