Sketchup will only take you so far and IMO it’s a waste of time if you plan on animating or interacting with the city later on. I recommend learning Blender, which will open many more doors for you down the road. The beauty of Blender is, there’s no limitation, no “dang, I guess I need to shell out $$ in order to get this or that feature”; you don’t feel like you’re getting ripped off because you didn’t buy the “pro” version. Sure, it might be harder to learn at first, but you’ll be rewarded at some point. You can even import models created in Sketchup to Blender, assuming the creator exported them in Collada or obj format.
If all need is a very simple city square with low-poly buildings and such with no need for animation, go ahead and try Sketchup. Personally, I wouldn’t waste my time with it.