@Doll: I think Cool Breeze just asks for the colloquial translations of English idioms.
Here are the Vietnamese version of some sayings:
VI: Nhập gia tùy tục. (When you join a family, you must follow the family customs).
EN: When in Rome, do as the Romans do. VI: Thà làm đầu chuột còn hơn đuôi trâu.(Better be the head of a mouse than a tail of a buffalo).
EN: Better be the head of a dog than a tail of a lion.Tre già khó uốn.(You can hardly bend an aged bamboo).
You cannot teach an old dog new tricks.Lợn lành chữa thành lợn què.(To turn a healthy pig into a lame one).
The remedy may be worse than the disease.Nuôi ong tay áo.(To keep bees inside one's sleeves).
He who brought up a crow to pick out his own eyes.
...
There are many else VNmese equivalent proverbs but I'm quite lazy now :D