Rochelle's about an hour from Sleepy Hollow (about 10 miles south of Crystal Lake). Davis Junction would probably be about the same distance, but I'm not sure how accessible it is anymore. I doubt you'd see much anyway. Outside of IRM, there really aren't many densely active lines up in that area. The CN (ex- IC) line to Rockford might see a few more trains than most of the other freight lines up that way, but you're still looking at one or two movements per line, while the sun is up. Otherwise, you're going to be stuck driving south, west or east to reach anything with any sort of decent activity.
:
I know everyone says go to the Chicago area to see lots of trains, but that particular part of the Chicago area just doesn't see the activity levels present to the south/southeast of the city. But don't let that stop you from enjoying your visit to IRM. I hear it's quite the place.
