Personally, I don't. I live in Boston, and lots of people don't pronounce their Rs (it "pahk my cah" as opposed to "park my car"). I personally think that accent sounds trashy as hell, and contrary to popular belief, not everyone in this area talks like that; more just the lower class people in certain areas. My relatives in Germany on my mom's side speak with a Bavarian accent, which I think sounds terrible as well. I don't have an accent when I speak English (in terms of American English, of course) or German.