When I was a commuter, I regularly had dinner at Union Station on the two nights a week I went to the gym after work. I sampled lots of places, both upstairs and downstairs. I generally got stuff at the fast food type places, and sometimes even at it on the train, as I usually wasn't there long enough to bother with table service. And as long as I kept my bag from Pret discretely closed up, I was never bothered about bringing it into the Club Acela while I waited. But maybe that was because I was a regular, and the attendant knew me by name (but she still scanned my AGR card every time I came in.)
I don't think there was much of a dropoff in patronage in the food court up to the time I retired (March 2019). There's been a lot of turnover of eateries, though, especially since the 2008 financial crisis. In my experience, one of the biggest groups of customers at certain times of the year are the school groups visiting Washington. I think that the charter buses can park upstairs in the garage/bus station and it seemed like the kids got some sort of meal coupons they could use at their choice of eateries. These trips usually happen during the spring, as is typical for school class trips in general. For some reason, the places upstairs (Pret a Manger, Cava, Chop't, Au Bon Pain, etc,) don't seem to appeal to middle school kids as much as the places downstairs.
I passed through about a week and a half ago (I'm going to write it up in the travelogue section), and maybe half the food places were open. All in all it was pretty quiet, but I was there in the middle of the day.
