I'm running a php app on a Mac Server OS X 10.6 with fully functional apache 2 server. The app is intended to run in Mexico, but there's no es_MX locale on the server. How might I install it ?
This SU answer might provide the info that you're looking for:
Assuming you know the appropriate values for the locale that you're setting up, you can make a copy of an existing locale and edit to include the locale-specific values.