disney..I dont know if this answers anything for you, but, if it were me, I would plant 9 garlic plants per square. Then, I always follow the basic rotation of fruit/root/leaf. If you plant a root(garlic), you then would follow that with either a leaf(ie spinach, lettuce, etc.)or a fruit(beans, broccoli, tomato, etc). So, you then get this natural pest control, and you get a good and safe rotation per each square foot...just an idea

I planted garlic in my sfg this week, this is my first year, my garlic came from the grocery store, was that ok?

It should be just fine

If it wasn't sprayed to keep it from sprouting.

I'm suprised this post I had started got bumped back up. For store bought, I actually planted half of my garlic this fall 14 with organic hardneck garlic I had bought at my local store. Sprouted no problem for me.

I agree with snibb regarding crop rotation. But since garlic is a great companion plants for Tomatoes or Eggplant, I suggest you consider planting garlic in the front squares and Tomatoes and/or Eggplants behind it during the same season.