American University has a great track that is open to the public. I did a lot of workouts there once upon a time. It's also reasonably close to Bethesda, so the commute shouldn't be too difficult.
Cardozo High School has a good track that is highly trafficked by the public, although that might be a hike from Bethesda. It also tends to have odd hours, randomly being closed at seemingly normal times. If it is closed, you can jog a couple extra blocks to Banneker, which has a free public track that is in decent shape and very circular.
AU is *typically* open but has been closed for over a year since Covid started. Security guards will kick you off.
Cardozo is open until 3pm. They lock the gates after for compliance but if you hop the fence they don’t care.