I've had the same problem over the years. Other than finding a good rehearsal spot or spending a whole lot of money sound proofing the garage there isn't anything you can do... cheaply.
However, there are a few things you can do:
1) Find out who complained and go to them and apologize. Then find out when they are home and when would be a better time to practice. If you are playing at 10pm (or 3am) find a better time... be a good neighbor. A short note a few days later apologizing (and signed by the whole band) helps too. Schmoozing gets you everywhere.
2) If you practice with a PA... turn it off. Or down. Get the drums off the PA. If the drummer is the loudest instrument, everyone else should be "just loud enough" to hear themselves over the drummer. Good dummers understand dynamics and can play at a reasonable volume... even metal drummers. I have been playing drums for a while and I use "hot rods" instead of those big baseball bats folks seem to like. My daughter (also a dummer... and better than me at 8 years old) uses jazz 7a's and she can play very quietly... or loud as hell.
The volume competition needs to stop. We all do it... I'm guilty of it too. A band does not need volume to practice, rehearse, or write. Have a talk with your bandmates.
3) Sound proofing. If your garage isn't finished you may want to ask the band to spend a Saturday helping to insulate and drywall. Expensive, but if you get the noise under control it is cheaper than renting space. Also, turning your space into a "studio" makes for a more creative environment.
4) Rent a space. Contact a commercial Realtor. Tell him you want to rent on temporary basis a commercial space that is currently not being rented. You agree to leave as soon as he rents it. I have done this in the past. I was in a band that need a space... there was a storefront downtown that was in a kind of out of the way location and hadn't been rented for six months. I contacted the Realtor and told him I wanted to use it for rehearsal space. He let us use it for half of what rent normally was... he just wanted the space to make some money. We agreed to keep it neat, not play after 10pm, no alcohol on the premises, no parties and such. We agreed to leave in 24 hours notice. We were there 3 months. It works great... for a working band.
Good luck to you... the good news is- someone is listening!