Hey Tim, sorry to hear about your ich outbreak. Some good advice given in this thread, hopefully you'll be successful in saving your fish.
Regarding garlic, garlic has indeed been proven to have anti-bacterial, anti-fungal, anti-parasitic, and antiviral properties (Bartelme, 2003 and Cortes-Jorge, 2001). Over the past decade there has been a number of studies involving garlic and fish food and the anecdotal evidence with regards to feeding fish allicin complex (the active ingredient in garlic) to rid them of parasites appeared to be quite strong. The following is a link to a more recent study that confirms what some people have been saying all along.
http://www.scielo.br/pdf/jvatitd/v12n2/v12n2a03.pdf
A. M. Shalaby et al. EFFECTS OF GARLIC (Allium sativum) AND CHLORAMPHENICOL ON GROWTH PERFORMANCE, PHYSIOLOGICAL PARAMETERS AND SURVIVAL OF NILE TILAPIA (Oreochromis niloticus). J. Venom. Anim. Toxins incl. Trop. Dis., 2006, 12, 2, p.196
In this particular study the inclusion of garlic powder at a rate of 3% was shown to increase the overall digestibilty of protein, carbohydrates, and fat, as well as to lower the total bacteria count within the intestine, muscles, as well as the tank water itself.
Garlic is a great preventative solution to keeping your fish (and water) free from outbreaks of various disease causing pathogens, and while on its own it certainly won't cure a case of ich, it's no snake oil either.