Hard Times Cafe on Nelson Street in Rockville. About 1/4 mile from Exit 6 off I-270.
Rockville Town Center isn't close to 270 so it wouldn't make sense from your perspective. Would add too much time to get off 270 and back on after the stop.
If you're thinking Gemantown, Greene Turtle is probably the best bet. Close to the Route 118 exit off 270.