I was just in Kotor, Montenegro last week, just for a day (a port call on a cruise ship). I didn't notice a significant Muslim presence there, in sharp contrast to my three days in Istanbul, where the prayers blare on loudspeakers several times a day and the restaurants were packed the minute the sun went down due to the Ramadan daytime fast.
The Bay of Kotor is a Christian area. Most of the Muslims are south near the Albanian and Kosovo borders.