Nong Mine is right
AFS is randomly placing students. However, statistically AFS participants who come from the urban area are more likely to be placed in the rural or suburban area, while AFS participants who come from the rural area are more likely to be placed in the urban. Again, this is just the statistics and it couldn't mean AFS places students base on this information.
Moreover, what you wrote on your application also affect the decision of your host family. Because in every area team, they all have urban, suburban and rural environments and it is also base on their ethnic background whether who they want to host.
Anyway, it depends on many factors. No direct conclusion for this!