I do not this that you have any "correct" or "bad" way, it is mostly based on your application design and requirements.
However, you may have noticed that in MongoDB 2.6.x the Full Text Search feature supports multi languages indexing and search if you specify a language in a document. This allow you to search text by language.
Documents look like:
{
_id: 1,
language: "portuguese",
original: "A sorte protege os audazes.",
translation:
[
{
language: "english",
quote: "Fortune favors the bold."
},
{
language: "spanish",
quote: "La suerte protege a los audaces."
}
]
}
for more informations:
http://docs.mongodb.org/manual/reference/text-search-languages/#text-search-languages