restaurants around Marriott City Center/one adult within walking distance??

You're in great shape as far as food goes! You can walk to the 112 Eatery easy, and if it's just you, I highly suggest sitting at the bar. It's not super cheap, but not fancy either (their burger is legendary! Same with the foie meatballs), and truly one of the best restaurants in all of the Twin Cities. You're a longer walk or a cheap cab ride away from Smack Shack (lobster rolls, great cocktails), The Freehouse (brewery with awesome casual food), Parlour(craft cocktails, more casual than it's big sister Borough, which is upstairs) and Bar La Grassa (Italian and a little more $, but you could get out of there for less than $30, depending on how much you drink!). The The Depot Tavern is very close as well-- super casual, pretty cheap, lots of great beer and right next door to First Ave/7th Street Entry-- legendary music venues in town. Have a great trip!