Over the past 17 years I've lived in three houses (in the suburbs of two different cities in two different states- one East Coast, one land-locked) and an apartment in NYC (obviously also East Coast). In all of the East Coast spots (urban and suburban) there was a mosque closer than the nearest McDonald's. For the land-locked state suburb the mosque was 2 miles away and the nearest McDonald's was 0.75 miles away.

I'm not selecting these houses to be convenient to the Mosque- I've never been in any of those Mosques. It's just an artifact of living in the sort of neighborhoods that I like. I tend to agree that it isn't urban/rural per se, as much as it's Openness of the Big Five personality traits. Which, at least in the US, tends to be correlated with a lot of other things (college education, density of living, etc.).