Translation:Это цирк, а не кафе.
Russian Ring-Masters obviously do not take kindly to loitering
Why are you drinking coffee in here? Stop it! Pay attention to the show!
Usually one would say it vice versa.
Can "а" and "не" be switched, or is this word order necessary?
no, а and не cannot be switched here.
just for information: Это не цирк, а кафе means the opposite - This is not a circus, it's a cafe