Welcome to the great outdoors!!!
One of the beauties of the garage is that you can hose down everything, or at least spill a bit, and there is no real issues.
However, you seem to think that in the winter time, you will be without water due to your climate.... however, I think you are incorrect.
I live in Michigan, and I brew A LOT during the winter, and I use an imersion chiller. The key with the hose is to drain it. Essentially, you do not turn the water on until you are ready to run water thorugh your chiller, and when you are done, remove the hose from the chiller and disconnect it at the spigot, and lay it out on the driveway Most drive ways are not perfectly flat, and slope away from the house in some fashion. You can make use of that to let gravity drain your hose. Then just coil it up and either keep it in the basement, or hang it in the garage. However, you may wish to attach a hose to the outlet of your chiller to direct that water into a snow bank and not the driveway... otherwise you may wind up with an ice rink for a driveway. Same rules for draining that hose applies, however, I just have a long piece of tubing I clamp to the end of my chiller to direct it to a snow bank.
However, any thoughts of puting hose water into your kettles for anything other than cleaning, is a bad idea. Most garden hoses tend to emit a foul flavor to the water that you do not want in your beer. If you wish to use the spigot for a water source for the kettles, however, you can adapt some tubing or buy some RV hose that are white... I understand that those do not give off the flavor that garden hoses do.