Julie2013
I've just a little worried about my oral English. May not be as good as native speakers.
Diversity > Fluency in oral English
I don't think it matters that much as long as you can get your point across. During my campus visit, I met a lot of students from non-native English speaking countries and they were communicating just fine with their accents

. I think they would value diversity over fluency in oral English.
If MIT Sloan is interviewing you, then they would have seen your GMAT, GPA, etc. They know that a person of such caliber can pick up fluency in a language soon and that shouldn't be a reason to reject them.