I ride to the dentist all the time (well, about as often as I go which is a couple of times a year). It's just off a couple of commute routes for me. They're quite accustomed to me parking my folder in their office. I've even done the road bike a couple of times and they don't mind.

I don't think I could ride home from giving blood... or give blood in the first place. I nearly pass out simply from having blood drawn for tests!