Oh, now I understand your situation. All you can do this year is push your launch date as late as 31st Street will allow and try to get more specific answers from them about the operational state of the harbor. Longer term, not being local, 31st Street is probably not the ideal place to store your boat for the winter. Almost any of the other yacht yards in the city would give you the launch date flexibility you need.
From the yards along the Calumet River you have only two bridges to deal with and I think you can launch pretty much whenever you want. From the yards on the Chicago River (south branch), if you go mast up, you will deal with 24 to 26 draw bridges and are restricted to groups of 10-20 boats on Wednesday and Saturday mornings, reserved in advance, from early April to mid June. Mast down, you can pretty much chose any day, though they sometimes prefer you avoid Wednesday or Saturday. There are mast stepping services at Burnham Park Yacht Club and Columbia Yacht Club. Something to think about over the summer.