I concur with Ravells. If you have a vector program use it.. though it is a bit different than PS. If you have never used a vector based program you might be better off with PS or any app that you know, unless you have the time to get to know the new app.
If you do go with PS, you can always break the city down into sections, work on the smaller sections, then near the end combine the various parts into the final map.