Tommy Robredo, seeking his third title in three weeks, also advanced.
Monfils defeated Bellucci 7-6 (7-4), 6-7 (5-7), 6-1 on the clay courts at the Fairmont Acapulco Princess. He will next meet Leandro Mayer, who was a 6-4, 7-5 winner over Carlos Moya.
Robredo stormed past Kevin Kim 6-2, 6-0 in their second-round match. Robredo has won tour stops in Brazil and Argentina over the past two weeks. His quarterfinal opponent will be Jose Acasuso, who advanced with a 7-5, 6-3 win over Juan Ignacio Chela.