The Chilean former Top 5 star last won the event in 2009. He got off to a good start this year with a 6-4, 6-4 decision over Spain's Riba.
Gonzalez didn't show any ill effects of missing most of the 2011 season with a knee injury.
Fifth-seeded Albert Montanes also notched a first-round victory Tuesday, handling qualifier and fellow Spaniard Ruben Ramirez Hidalgo 6-2, 6-4.
No. 7 Carlos Berlocq of Argentina advanced with a 7-5, 6-0 victory against Spaniard Daniel Gimeno-Traver while Federico del Bonis of Argentina bested two-time Vina del Mar finalist Nicolas Massu 6-0, 6-3.