Turning the battery off is a good idea for a period like that to prevent drain by alarm, clock, radio etc..
However, a much better idea if you have power in your garage is to invest in and connect to a battery conditioner (e.g. CTEK). This would mean the alarm remains activated, the ECU doesn't need to go through another learning process, the radio doesn't lose its memory and need a full reset, you don't have to leave the windows down so you can open the doors without reconnecting and it's better for the battery being periodically topped up at optimum points.
I have cars and a bike I leave lying around for weeks connected to battery conditioners. Before I connected to conditioners (and leaving the batteries connected) I got 2 to 3 years out of a battery, after leaving them connected I get 9 to 10 years - the conditioners paid for themselves.