Scott,
In my experience, if any of the controllers will have different configurations, each of them will need their own AMP group.
Therefore a pair of redundant MAsters can be in their own AMP group and I would put each of the locals in their own AMP group.
You can create folders for each of them or how you see fit and split them up by regions, etc..
This is if you only plan on performing configuration changes from AMP itself, if not, then don't bother will mutiple AMP groups but if ever you want that in the future, set yourself up for it properly now.