If you can't test ride the bike, then you'll never know if you are comfortable on it. Did they do a professional fitting on the bike? If they're serious about selling you a bike, they'll put you on it and measure your bends - back, knees, elbows, etc. Then, they adjust the bike to fit you and you take it for a test ride and see how it feels. Go back to the shop with the free maintenance and ask for a manager. I can't believe they won't let you ride one!! It's not uncommon (nor unreasonable, IMO) for them to ask you to leave either a credit card or a drivers license, or both. I wouldn't get upset about it. They're just protecting themselves..