Assuming both win in the quarterfinals, we'll get Costa Rica in semifinals anyway.
Not that big of a deal; but, our opponent will depend on the outcome of the Jamaica/El Salvador match (assuming that Mexico does not lose to Curacao by more than 2 goals).
If El Salvador wins outright, I believe we get Jamaica.
A draw and we get El Salvador
A Jamaica win by more than 2 goals, we get Honduras
A Jamaica win by less than 2 goals, we get El Salvador
A Jamaica 2-0 win, we get Honduras
A Jamaica win by exactly 2 goals and El Salvador scores more than 1 goal, we get El Salvador.
A Jamaica 3-1 win, it goes to drawing of lots between El Salvador and Martinique for the final spot. We would get El Salvador if they win the draw and Honduras if Martinique wins the draw.
I think there is a way for Mexico to finish 3rd in their group and we'd face them in first knockout round. El Salvador must beat Jamaica in the early game. Then, if Mexico loses in the late game by more than Jamaica lost by, Mexico drops to third and is our opponent.