The problem is that by default it is showing the default city. Therefore, the user will have to click on the drop down arrow and choose select city or start typing. Some users will not do this and they will be given the wrong city designation. Other users will get confused when they do not see their city on the list. Not to mention, this adds extra clicks that users do not want.
Leaving this field blank will prompt them to start typing their city, and then the plugin can recommend one that is there already or create a new one. This would prevent confusion and errors.
In the end, you can develop the plugin as you see fit. I do not want to be a pain in the arce. I just want to provide some feedback that I know will make this plugin great!
Kind regards.