There is no allowance for the carry of a loaded handgun for personal defense by any person Unless you have a valid Illinois Firearm Owner Identification card (FOID).
Even the FOID card only allows loaded carry for such on your own land or fixed place of business. For personal defense even FOID holders must carry unloaded and cased.
In Illinois open carry (loaded or unloaded) in unincorporated areas of the state have traditionally been considered lawful, but Continued changes in state law over the last 15 years have made doing so felonious under most circumstances. Under Aggravated Unlawful Use of a Weapon the exemptions are limited and self defense is not one of them.
Even possession of an uncased firearm in your hotel room or a friends home currently can be prosecuted as a felony in this state. Most counties would not prosecute but Cook County Has and the convictions have been upheld. Corrective legislation is on the Governor's desk, hopfully he will allow it to become law.
In a nutshell, You are limited to broken down in a non functional state or cased, unloaded and not immediately accessible.