How about this link for calculations?
http://www.kusat.com/install/calculator.php
There is also a piece of software than can give you your skew angles. I found on another site. Hopefully it has specs for Mexico.
http://www.arachnoid.com/satfinder/
And online version.
http://www.arachnoid.com/satfinderonline/
Heres a google style map with various aiming angles.
http://www.dishpointer.com/
There is a marker on the map that you click and drag.
