You'll find Calvinists in Baptist Churches and in Pentecostal churches---but you will also find some of these churches to be decidedly anti-calvinist also---I'd say it depends on the church.
You won't find too many calvinists in the methodist churches, or even in Lutheran churches(which I find somewhat odd),
Outside of the Presbyterian church, I would think that most calvinists you find are either Baptist or Pentecostal of some sort....
But the largest majority of Calvinists seem to be Presbyterian for sure......and I know that to hold office in the Presbyertian church, you must hold to certain creeds that would make you calvinist, like the Westminster Confession, for example.
My pastor is Calvinist, and Baptist, for the most part(he pastors a community church but we are part of the General Baptist Convention and American Baptist Conference). I would think that most, if not all of our elders are also calvinist, but I'm quite sure that not everyone sitting in the pews is! Even though Pastor Tim made his views on the Doctrines of Grace quite clear this spring......
At any rate, he didn't have to be calvinist to lead that church, it just so happens that he is(Praise God!).