The apparently unique (and dirty) method to have conditional fields depending on a taxonomy field, it’s to create a separate group fields and display it using location rules (Show this field group if : Post Taxonomy IS EQUAL TO taxonomy_I_will_choose).
It’s not good AT ALL. But it’s the only way for the moment.
Besides being impractical and doesn’t work on front end form (which is a shame), it’s buggy : when you choose a taxonomy on a post, conditional group field appears, ok. Then you save the post and after that, you want to edit this post. Now, if you change your taxonomy, group field link to previous taxonomy remains displayed ! And sometimes, if you save, errors appears.
You should really fix this conditional fields on taxonomy !
Conditional logic for taxonomy and other fields has been discussed here before and the developer has said in the past that he’s working on it. I’ll mark this topic for him to take a look at. He has a lot on his plate.
In the mean time, my suggestion, if you really need to have conditional logic based on a taxonomy would be to use a select field that has dynamically generated choices. http://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/
I’ve needed this as well, so I created a custom field setting which allows for conditional logic based on taxonomy. Give it a try when you get a chance.