We've been on an escarole kick but it's not the easiest thing to find. We've found it occasionally at the whole foods on Wisc Ave but would love to know a place where they always have it.
Balducci's in Alexandria has some varieties most of the time, especially frisee. Maybe the one in Bethesda does too. We are getting into early lettuce season at Farmers Markets, so maybe try one of them.