Starting from a city generator and then retouching the result in photoshop is the only shortcut I think could work. "Quick and easy", however, remain relative terms even in that case when speaking about cities.
There are various options, like:

Roleplaying City Map Generator » Inkwell Ideas

Roleplaying City Map Generator - Software Informer. Create unlimited maps of any kind of villages, towns, big cities for roleplaying.

There was one (or more?) tutorial somewhere in this guild on the topic city generator + photoshop (or Gimp)