I was able to delete the extra downtown finally. I had been looking for the trash can icon in the original "choose a downtown" screen you get when you start your play session. Once I found the screen where you can add a new downtown, the icon was there. Bad news
- I deleted the wrong downtown. Good news
- I hadn't spent much time fixing it up, and no one owned a business there.
What would have happened if I had deleted a downtown with an owned business? Not that I want to experiment.