If by "hot water heat" you mean you have a boiler and that is where your heat for your house comes from that can be both good and bad.
I have no idea what humidity is like in Illinois, but if humidity regularly gets above 60% then in general your best bet is to encapsulate your crawlspace.
Seal all vents and I do not mean just close them but SEAL them completely with at least 2" of rigid foam board insulation sealed in with "closed cell" spray foam.
Cover and SEAL the ground with preferably 12Mil Polyethylene sheet, if you want it to last more than just a few years then buy quality "virgin plastic" it should last probably 50 years.
There are a few ways to finish, the best "in humid areas" is to take down all the crap fiberglass batting from the joist and throw it away.
Get polyiso rigid foam board insulation that is R10+ and cover and seal all walls in the crawlspace and foam it in with closed cell foam.
IF you do not have a HVAC unit (Plenum) in your crawlspace then you "might" need the dehumidifier you were talking about, but a decent one large enough to properly do a crawlspace will run about $1400 plus you need an outlet that may need to be installed plus the electricity to run it continuously, plus the maintenance of it, plus you need to check them regularly at least once a week. In other words a hassle and expensive.
IF you do have a plenum/HVAC then simply open a hole and install a vent and your crawlspace is pretty much conditioned.
Prior to encapsulating my crawlspace I could stand in the middle and literally hear it RAINING under the house as the hot humid air sucked in and condensed on everything.
Was a total nightmare under there.
Now it is like walking into any room in the house, DRY, stays between 68-72 all year.
http://www.crawlspaces.org/
http://www.advancedenergy.org/portal/crawl_spaces/pdfs/Field Study - 2005.pdf