Haha, oh dear. Chicago geography.
I don't know that it's completely necessary to nail down where the office is - other than it's somewhere "bland." I mean, we never really know where Harry Dresden's apartment is, other than it's somewhere in the city, with protagonist-magic access to Michael and Karen's houses.
I could go into a long, rambling discussion of Chicago's neighborhoods, but I think it'd be fun to put the Group in the Ukranian Village, if only for some of the Group's members having to puzzle out exactly what they're eating for lunch after they order on a menu that's mostly Cyrillic.