There is a tiny Whole Foods on River Road just above Arlington Road (in the small commercial strip that also has several gas stations, American Plant, a beer-wine store, McD's). It has a limited selection, narrow aisles, and the parking lot is like a war zone. The county really should never have let them put this store in this location. On days like this - a day before Tday - the traffic on River Road backs up in both directions with cars waiting to get into the lot.
About five minutes away, there is a much larger (double the size?) Whole Foods in Friendship Heights with a big underground parking garage and yes, they do validate your ticket.
I assume that Whole Foods keeps the small store open because it does a lot of business but why does it do so much business? Shopping there is such a huge hassle!