Currently it seems MOST NPCs only speak english (with some also speaking mash).
I would propose that NPCs that remain in a specific borough should also speak the thematic language of that borough, while NPCs that frequent it should also speak it (probably nowhere near fluently though).
The idea here is to allow for even more use of language than currently exists, and create opportunities for players that are attempting non-english playthroughs to have access to at least some of the same coded systems that are in place for newbies.
Borough Examples
San Mayo - Spanish
Little Koyoto - Japanese
Gulag - Russian
Chinatown - Tagalog
Green Central - Euro
GATO
