Medicare Supplement Plans, All equally accepted on the road?

My school also offers regional plans, but we wouldn't be interest in them. The three supplemental plans we'd be interested in all state that they are for people who live anywhere in the country, and will be accepted by any doctor or hospital in the country who accepts Medicare. I'm just wondering if providers out west will balk at Tufts or Harvard Pilgrim which are known in New England. Both of those plans appear to be a bit better bang for the buck than the Blue Cross Blue Shield plan offered.