Very preliminary googling shows that there's a free 50-acre garden in Silver Spring/Wheaton -- Brookside Gardens [link] Depending on weather, obvi.
Tons of good restaurants around, so the world is your oyster. Or taco. Or bibim bap. You get the idea.
I'll check for other options, too. It'll be like a "check out your own local area day... " I'm never in Silver Spring.