If you are looking for an accommodation that is located near great public transportation (metro and buses) sites, food shopping and restaurants all within a short walk; this is your place! We took the Metro from DCA to the Columbia Heights station (1 transfer required on the weekends). If you are going to lean on public transport, I highly recommend buying a Metro pass. We did rent a car, but that was only to drive to Monticello. The parking pass that comes with the unit is handy for that, but I wouldn't want to have to find parking on a daily basis.
Carlton is VERY responsive when emailed or called. We had some WiFi problems when we arrived and he responded very quickly. The Apple TV is a nice touch too. The combo lock on the front door is great as anyone in your party can come and go, and you don't have to worry about who has the key. Getting used to the NEST thermostat took a little doing, as I've never used one. The beds are VERY comfortable.
Shopping for last minute items the CVS is a 5 minute walk. If you want to lay in food instead of going out for all your meals, the Giant Supermarket is likewise only about a 5 minute walk. Lots of great little restaurants and eateries within a 20 minute walk of less.