Thought I'd follow up with some information that might be useful to others. First, the location that ended up working for the event I'm helping to plan is Connie's Pizza on Archer Avenue in Bridgeport. We picked one of the three available pizza menus for groups that will feed our group of (now) 30 with thin-crust veggie, thin-crust pepperoni, and deep-dish sausage for less than $500 and leave some money for pitchers of beer. The event is in July; I'll try to remember to post back on how it meets our expectations.
The other contender, Portillo's on Ontario, said that they were booked up with private parties throughout Taste of Chicago (July 10-14). We couldn't change our event to another week, unfortunately.
"Your swimming suit matches your eyes, you hold your nose before diving, loving you has made me bananas!"