First we need to know who a Buddhist before we can tell if they can exist amongst many Catholics.
Buddhist are people who definitely do not believe in God. They are not christian. They pay reverence to "Buddha" who is known to be the founder of "Buddhism".
Their way of worship is similar to the catholics in the sense that they bow down to worship the image of Buddha, the way catholics bow to worship the image of Mary.
So both Buddhist and Catholics bow to graven image which is out of the doctrine of our Lord God.
Exodus 20:4: Thou shalt not make unto thee any graven image, or any likeness of any thing that is in heaven above, or that is in the earth beneath, or that is in the water under the earth.
So then it does not matter if one is the only Buddhist amongst catholics because they both worship Idols.
It is forbidden for us to make a graven image and be worshipping it. They don't know the implications because they are ignorant.
But if you want to be part of the true doctrine of our Lord God, You can give your life to Christ
