My friend interviewed at a scooter shop in Denver. She showed up in a motorcycle jack carrying a helmet in gloves. The interview was more about her scooters than anything else. She has 5 or 6 vintage Vespas, she got the job.

Definitely ride the bike. Clean it, but make sure it looks like it gets ridden. If needed, replace tires, brake pads, bar tape etc... Make sure everything is in perfect working order. I'm not sure I would ride any of my bikes to an interview at a bike shop.