In Linux Mint 4.0 Daryna the mint tools were only in English. We’ve worked on this and internationalized these tools. The community then translated them and we’re now in a position to say that Linux Mint 5 Elyssa will fully support the following languages: English, French, Spanish, German, Italian, Polish, “Brazilian” (as in pt_BR), Russian, Swedish, Turkish and Ukrainian.
10 other languages (Bulgarian, Danish, Greek, Irish (gaelic), Norwegian “no”, Norwegian “nb”, Dutch, Portuguese (pt_PT), Slovak and Serbian) are also partially supported. For these languages some of the tools were not translated yet.
Other languages are also supported by the system (as in previous versions of Linux Mint) but with the mint tools in English.
If your language is not fully supported don’t hesitate to translate the tools yourself. It’s easy and you can do this directly from the Linux Mint forums: http://www.linuxmint.com/forum/viewforum.php?f=43