Portugal's next game in the Confederations Cup is against hosts Russian Federation on Wednesday before the European champions conclude Group A against New Zealand on Saturday.
For Portugal, Ronaldo is supported by Nani and Ricardo Quaresma up front, while West Ham United defender Jose Fonte starts at the back alongside Pepe who is yet to find a new club after his Real Madrid contract recently expired.
"If we apply it to perfection we have a very good chance of beating Portugal. It was a great result for Mexican football".
Portugal coach Fernando Santos said it was not the performance he expected from his team.
The guy just scores goals.
He attracted headlines last week after being accused by a Spanish prosecutor of defrauding the country's tax authorities.
The teams went into halftime tied 1-1.
Ronaldo made a great run from near midfield to set up Quaresma's 34th-minute goal.
The Euro 2016 winners took the lead on 34 minutes when Ronaldo sprinted into the box and his beautifully-timed pass found Quaresma unmarked in the area. However, other than that he did not threaten Mexico goalkeeper Guillermo Ochoa.
When Ronaldo's volley thumped the crossbar, Nani pounced on the rebound, but the video ref spotted that four players were offside.