Metra also has some new (well, refurbished actually) bike cars, where they have taken half of the lower-level seating area and made it a dedicated bike area. I am not sure what the limit is but based on the videos I've seen, it appears to hold quite a lot. These run on the Milwaukee North and West lines and possibly BNSF route too so not all lines have them yet.
+2 on the bungee cord method of securing bikes. Some conductors are sticklers about having the bike secured, some aren't. Best not to chance it. Be prepared.
Oh, a funny story.... I was at one of the suburban stations and a group of kids/teenagers with bikes showed up ready to board the next train. They decided to split up so no more than two would be boarding the same car. When the train arrived, some of the kids boarded with no problems, but at least a couple of them were turned away by the conductor. I didn't hear exactly why he wouldn't let them board, maybe they weren't old enough? But they were left there on the platform with their bikes as their friends rode away on the train without them.