[Plugin: Ajax Post Filter] sub category support?

Would love to be able to display a list of taxonomy subcategory filters of a defined top level category. My use case:

I have a taxonomy of cities – I would like to be able to associate a subcategory of postal codes with each city category. Then display those postal codes as the filterable list. Ideas? Maybe a tweak to the existing plugin?

https://www.ads-software.com/extend/plugins/ajax-post-filter/