You can see in the table below the results of the plebiscite.
Here's the interesting part. Two weeks after the vote, the Commision on Elections issued a resolution declaring that Ifugao will form the Cordillera Autonomous Region since it's the only province that voted positively for autonomy.
Then president Corazon Aquino was also amenable to the idea of a Cordillera Autonomous Region comprised of only Ifugao.
However, in December of that year, the Supreme Court ruled that a single province can't constitute an autonomous region. That said, Ifugao wasn't made an autonomous region. It was returned as part of the Cordillera Administrative region.