We are using D6 with Organic Groups. Each group has location(s) tied to them in the group content type. Besides the Proximity search, we would like to also have an Exposed Filter that allows the user to toggle if the location belongs to a particular Group or to All groups.

I thought this would be easy at first to add a filter for Organic Groups, and the closest option is Posts, since this gives you the toggle-per-group option. But the Locations don't actually LIVE in the Group as a Post, so if you toggle Group1 OR All, no changes are applied.

So how would you create a filter to toggle between location "owners"?

I saw that there is a GMap Taxonomy module which I enabled, created a new vocab with 1 term for Group1, though in Views, I don't see a filter for GMap Taxonomy. So I tried the standard by Term ID but it just had the same affect as the Organic Group: Post filter which didn't do anything.