Is it alright to put a gun safe in a storage room in an attached garage? Do I need to buy one of the humidifier rods to go in my safe so that my guns will not rust? Any feedback would be appreciated!

Depends, how well insulated and sealed is the garage, I use silica gel in my safe that is in my bedroom closet. I keep my windows open almost all of the time and haven't had a problem with rust. Are you near a lot of water? If so then I'd say go with a goldenrod. You can buy a box of silica gel and see how that works for you.

will the safe be visible from the street/driveway when the garage door is open?

may be a quick way for a few guys to throw it in the back of a truck.....not sure that's a big concern.....but certainly could invite trouble......esp if you leave your door open often for a while....

Having seen the results of guns stored in a unheated room , I would say get the rod .

Make sure your safe is not visible when the garage door is open.
Bolt your safe to the garage floor.
I would use the goldenrod to keep the humidity under control but it depends where you live. If you are in Arizona maybe the silica is sufficient. but if you have a power outlet near your safe, just use the rod.

Keep all the steel parts of your guns covered with Birchwood-Casey SHEATH, (BARRIER)and you will have no rust no matter where the safe is! I used to keep my safe in my barn in upstate NY, and the SHEATH kept them all just fine. I never used a dehumidifier of any sort, and it rains there constantly!!

Buy the golden rod and install it. What does it cost in comparison to cost of safe and the guns you store inside? Better safe than sorry.

I also use the gun safe to store other things like my range finder, binoc, gps, etc. You cannot cover those with Birchwood-Casey Sheath.

Use the rod, it's cheap insurance!

I'd get the safe up off the concrete floor. Maybe up on a 2X4 frame on edge to create a small air space. Then bolt it to the wall studs through the inside wall of the locker.