First question to you: do you have a CCW endorsement? If not, get one ASAP.
Then, I would not OC anywhere in STL until SAPA gets passed into law, if it does get passed into law that is.
RSMo 21.750.3 provides for any political subdivision to "ban" OC and thus if your gat is viewed you can be arrested. So, when in STL county (IMO), with the patchwork of towns who do and do not ban OC, I would cover the gat. You literally could walk 10 paces, and transit from one town (OC OK) to another (OC not OK) without even realizing it.
Read and know RSMo 571 for a start. Really know the CCW sections. then, while sitting in your PJs at home research which towns in your normal area of travel is OC friendly and which towns are OC hostile. Once you cross the river, and I'm not talking about ILL-inois, then the research is easier and the number of hostile towns rapidly diminishes. St Charles is reported to be very "OC friendly" (code for the cops know the law).
As an example of the night and day attitudes from STL to the sticks, across the The Big Muddy, the Troy mayor flat out told the city council that they will not ban OC using RSMo 21.750.3.
Lastly, do not go armed into ILL-inois, ever. I would go as far as stating that ILL-inois is to be avoided for every reason or for no reason.