They get dressed up in wind-efficient sports clothing and ride their mountain bikes 3 miles to class--the frame alone costs $1000--and then ride home again having saved us from the evil CO2, and then pile into their noisy, bucking stinking little economy car to go to the mall to buy fresh mountain bike socks. Yes, they do. All their friends ride mountain bikes, too, unless it rains or is cold, which it is 90% of the time.
Actually, I see most of those types here in Madison, driving Volvos, Audis and the occasional Mercedes.