I think you should indicate earlier that you don't support cities before users go through the process of creating an account only to find out they can't use you

I think you should indicate earlier that you don't support cities before users go through the process of creating an account only to find out they can't use your service. I understand you want to maximize users and figure out where the demand is the highest, but I think you should at least give users the option to continue creating an account if their city is not currently supported.