What's a free app that I can use to get internet signal in Mexico?

Applications don’t get internet signals. That is a matter of the operating system and the wifi adapter.

Of course, just getting a signal won’t do much good unless you are allowed on the network and that is a matter of having the right credentials (username and password usually) and not one of software.

And that assumes that you are even someplace that has wifi.

skygrabber

@UScitizen
1) Not free (though the feature-limited trial is)
2) Requires a satellite dish and satellite modem so it cannot be used with a regular computer by itself.