Hi Bob,
I would think you would need to be careful with this situation. I am unsure if duplicate content problems can arise if the content is in two different languages. I think you nailed it on the head when you said one website with a translation button.
For localization I think it would depend on how far away these locations are from each other and if both practices are doing business the same way.
It is possible to add more than one location to directories with a single URL.
Hope I helped....