I want users to see other users near them. If I ask them to add their address other users know exactly where they live. If I have users enter their city, and multiple live in the same city, their pins hide behind each other. A couple of solutions:
When multiple users have the same location group the pin. When a user taps on a group of pins they spiderweb out allowing the user to view each individually.
Allow a general location option, similar to craigslist, where it shows a 5 mile (or so) radius of where the user lives.
I prefer solution 1, but I would be happy with either. Let me know if you have any questions.