After you fill out the Local Services Census at your event, have some people find the services that could be improved. We've got two tools that the User Experience volunteers in your group can use to help get them fixed up.
http://citizenonboard.com/ is a great way to make annotated screenshot UX teardowns of local services.
We also got 70 donated credits to UserTesting.com. Set up some videos of people trying to use these services.
After you do either of these, set up some meetings with the City department that is in charge and show them your work.