If quota is 17, I'd guess the number of women is about three times that. Just to be clear, though, being Greek at UIC is going to be a very different experience than at a Big 12 school. There are no sorority/fraternity houses (though some groups may have unofficial off-campus housing), for starters. All three NPC sororities are great groups and you can have an awesome time in a UIC chapter, but you may have to un-learn some of your existing notions of Greek life.
Phi Sigma Sigma has a house and live-in requirements.
There's an ice cream social on Thursday 4pm-7pm in Room 613 in SCE. That's kind of strange about the chalk on the quad though- September 6th is listed as the first day of recruitment by the CPC website, so I'm not sure why it says it's an informational meeting. I wouldn't recommend missing it either way.