What format are you shooting?
You can definitely come up with a concept to just shoot the people of the city. For example, you could do a project on a certain neighborhood or district of the city, then have each subject write something about themselves to accompany the photo. I know I have a lot easier time coming up with concepts than I do actually making them into photographs.
Not to plug tacky blogs, but here's a couple scans of a few projects I have done for school over the past semester or so, as well as the one I am currently working on: http://samreinselphotography.blogspot.com/