It's 21... much to the dismay of the teen girls who were sitting next to me at the bar, trying to order Pina Coladas.
The bartender kept saying, "Virgin coladas?" and they tried to act all cool and still order them anyway. This went on for several times, until he finally said, "virgin ones it is," since they were clearly too young. Then one of their KTTW cards had been cut off from charging, so they couldn't pay either. I think they were dying of embarassment.
Moral of the story: I don't think you can pull anything over on the bartenders at CC.