Idexx puts out a snap test that checks for heartworm, Lyme's, Ehrlichia and Anaplasma exposure. I'm not sure how long it takes before there are enough antibodies to trigger a positive test, but I believe it can be done sooner than a titer. Your vet might have a better idea.
If you were in urban Chicago, though, I wouldn't expect there to be many ticks. In a suburban area or the country surrounding the city, though, there might be. The ticks are pretty bad around here this year, but we're also a few hundred miles north of Chicago.