I would bet that in most cases, if a truck and a group of guys capable of loading a full gun safe show up at your garage door, they already know you have a safe and that's what they're after. No amount of camo (fake cabinets, etc.) will help, they know it's there and they will find it.
I remember hearing of a fellow who had a huge safe in his basement. As I recall, it took 4-5 of his buddies to help him get it down the flight of stairs (empty of course). Unfortunately, he loved to brag about all of his firearms and how costly they were. Apparently, after returning from work one evening, he found that his safe, which had been filled with firearms was gone. This meant that the thieves carried it all the way back up the basement steps. He said that there wasn't even a nick in the paint of the walls along the stairs. It was as if no one had even been there. Nice that the thieves were considerate about that!
In my opinion, if you have no alternative, then the garage should be fine. Be aware of humidity and temperature concerns. In many cases (no pun intended), a dehumidifier rod or two will keep the humidity down and the temperature up enough to keep your firearms happy. Firearms do not have to be as warm as humans to be happy, just as long as the humidity is controlled.