In 1963, Villanueva was drafted into the United States Army, and spent two years in the Panama Canal Zone, where he became immersed in Hispanic literature, reading Rubén Darío and José Martí. He graduated from Texas State University, on the G.I. Bill, from the State University of New York at Buffalo with an M.A. in 1971, and from Boston University with a doctorate in Spanish in 1981. He has taught at Wellesley College, and held visiting appointments at the University of Texas-Austin, the College of William and Mary, and Bowdoin College. Until his retirement in 2015, Villanueva served as senior lecturer in Spanish, Department of Romance Studies in the College of Arts and Sciences at Boston University.