You may not be able to AC your entire garage, but you could cool an entire rack with a rackmount AC unit (tripp-lite sells them). It costs more since you are constantly having to cool hot air as it comes in, so it's not an ideal solution from a performance or affordability perspective. You can buy ducts to push the heat out, but garages typically have poor insulation so ugh.

I live in Idaho and keep my 24U rack in my office, total idle draw on it is now around 4A@110V and considering power tops out at $0.11/KWh during the summer there's no real reason to colo it somewhere else.