To place the labels once for each region you will need to create a second map with the labels where you want then use a dual axis to overlay them. In the image below I created a duplicate of the Region field and assigned it the geographical role of state then assigned which state a region should map to. If you want to be more precise you could select a city in each region and map to that point. Attached is a workbook with the example.
Region Labels.twbx 1.5 MB