My mom told me an interesting story recently: She is a retired lawyer - not in medicine - but her anecdote resonated with me:
Years ago, a legal job applicant indicated on his resume that he spoke two languages, in addition to English. Unplanned, the interviewer to whom the candidate was assigned also spoke those languages and proceeded to speak to him in those languages during the interview, only to find that the candidate spoke both poorly at best.
As you can imagine, the applicant was not hired.
I frequently see applicants indicate on their curriculum vitae or their AMCASes that they speak languages fluently. If you do speak a language in addition to English, good for you and great for your candidacy. However, if you indicate that you are fluent, please be ready for your faculty interviewer to conduct your entire medical school interview in that language if s/he pleases.