In a metro like Chacago, there will be a vast variety of meetings. Some lean toward an older crowd, some younger. Some will be more densely populated with people of a certain trade or profession. And they are available all hours to accommodate shifts and schedules. Don't be disappointed if the first one or two you try aren't a perfect fit. Check out a few.
The AA schedules usually give a clue as to the focus of each meeting...book study, or speaker, or discussion. No matter the type, the regulars will clue you in.