This is a great analysis of the actual location of a stadium and its average attendance. It comes courtesy of soccernewsday.com
Here is a link: ArticleI am not really sure what to make of it but to me it looks like there is not a strong correlation between the distance of the stadium to a major urban center (contrary to the writer's opinion).
However, there is a small paragraph on the Revolutions which made me feel quite good that at one point, the ownership and the wonderful legislature will find a solution for the team to leave the suburbs.
I know I am an eternal optimistic.
I hope you find the linked article (at least the data) as interesting as I did.
PS: if you are a geek like and are interested in attendance number for the MLS, bookmark this site: MLS Attendance