This is a basic question but can't find the answer anywhere.
My site has 4 defined languages en_US (default), es_ES, fr_FR and pt_PT.
If someone from Spain, France or Portugal access the site will have his own language displaying, but if someone from Mexico, Brazil or United Kingdom make an access the displayed language will be the default in my case en_US.
The question is:
To have the site displaying in Spanish for someone from Mexico, should I define a new language es_ME, or is there a way to make the browsers assume just the first two letters of the language code 'es'?