DR FJL - Glad to hear that you enjoyed
The Visit as well as your stay at Ritz-Carlton Pentagon City.
-Yes, the grocery store is "just outside", if by "just outside" you mean: going into the Pentagon City Mall, heading down to the Food Court, walking through the parking garage, going back up to street level at Pentagon Row, then walking across the big parking lot to the Harris Teeter.

*Did you try any of the restaurants over in Pentagon Row? Lebanese Taverna is one of my all-time favorites, as well as Thaiphoon. -However, the restaurant choices over in Shirlington by Signature ain't bad either.
**And as for the taxis - Is Signature no longer handing out the "call me a post-show taxi" cards? They used to do that at their old location since that part of Four Mile Run was usually deserted at 8:00pm. At least being near Shirlington there's a better chance of hailing a cab due to the restaurants and bars there.