My question to you is, are you working under a polygon count limit? If not then you should not worry too much about your polycount. By the way, your polycount for that current scene is actually 6653 (tris), if you triangulate your mesh both faces and tris numbers will match up.
Your computer should be able to handle it. My highest poly count was 170,000 (tris) and I had no slow down. I have 1 gig of ram.

About the topology...well, it's ok. but what concern me are the extra edges around the side buildings and the middle building. Many of these edges are, in my opinion, useless and do not help the shape of the object.
If you delete these edges it will decrease your polycount.
When you are creating the windows, then you insert the edges to create the window.
It's good to have an efficient model.