is biking lower wacker drive in Chicago a good/feasable idea?
Answer (tl;dr)  Find another route.  

I checked around using google street view to get the image in the question.  Some observations...


There are no cyclists visible anywhere.  There are also no motorcyclists I noticed.
The lighting is poor and patchy
Many of the vehicles travelling the lower deck do not have lights on.
The road surface is patchy and potholed
There are a lot of unforgiving kerbs and concrete barriers
The signage disagrees with itself (speed limit is 30 mph and 20 mph just along)
Access ramps are just as cycle-unfriendly as the lanes.
Plenty of cover if someone wanted to lurk in the dark and accost a hapless cyclist.
Culture of bogans, chavs, yobbery and dangerous driving later at night.


Street View has a real problem following the level - it pops you between levels on the same road, which leads to the point that there is an upper and a lower deck, that both follow the same course.  Why would you confine yourself to the narrow dark and dingy lower deck?  

The one advantage of the lower road is if its raining, you'll be covered for some of our journey.  However the cars will also be wet, making for slipperier roads and dirtier road spray.  The driver's vision will also be obscured to some degree, lowering your safety just as much if you were in the open.

This idiot has recorded a ride on the lower deck.  He's giving all cyclists a bad name with his riding style, and I see no lights at all.

                
            

Other Routes
This PDF has some useful info  http://chicagocompletestreets.org/wp-content/uploads/2016/01/2016-Chicago-Bike-Map.pdf

Here's a snip showing just the whacker drive area.  Franklin, Wells, Dearborn and State are all north/south roads with some kind of bike space.  Washington, Lake (?) and Harrison are all east/west roads with some bike considerations.  You've got some options.



Supporting Links

http://www.chicagotribune.com/news/ct-lower-wacker-drag-racing-met-20150717-story.html