I used to live in Olney (now just 10 minutes away)!
You can look at the Marriott in Gaithersburg at Washingtonian Center too if you want. We used to enjoy going to that area to walk around the nice lake and eat at the restaurants there. Never been to the hotel though.
If you do, avoid at all cost Lakeforest Mall. It used to be nice 15 years ago, but has gone way downhill and I wouldn't step foot in there now.