Since I’m going to Silver Spring, I take the S9 Express, but there are probably better buses to Bethesda–if you’re not sure how to put the bike on the bus, google bike rack bus or something like that, there are several helpful youtube videos.
I am working up to biking back, though–I did it once and was really worried about the uphill climb, but as someone else said, it really isn’t that bad–even for me, who isn’t all that in shape either.