Resident alien. Selling property in Mexico

There are already a couple of questions that answer my questions, but I have some specific ones:

 

If I sell a property in Mexico (no construction), do I need to report it in my Tax form and pay taxe...

 

Solved: Resident alien selling property abroad

 

Basic one: we still don't have the green card. As far as I know, this doesn't affect the fact that we have to pay taxes or at least report what was paid.

 

The taxes were already paid to the Mexican government. I think there's some agreement to avoid double taxation, but I don't know if it applies to selling land (this was plain land, no house, no farm, no nothing).

 

The exchange rate changed in the time we owned the land (in other words, the value paid when we bought was more in dollars than what it says it costed in MXN pesos). Is that even taken in consideration when calculating gains?

 

And assuming the answers from some of those questions, what we have to do is report the gains, and report the taxes paid to the Mexican government, correct?