Steve, you can grow garlic in SD, almost year around.
If not the bulbs, you can use young garlic greens and stems in cooking. Maybe you can try and experiment a few in a partial shade cool spot now, just for the green like leeks.
I plant mine here (GA_z8) in OCT-NOV.The early ones are almost the size of leeks you see in supermarkets(but not as thick). Thesedays I just pull one up and use fresh young garlic.
You may think that weather in GA is warm ! But it is not where I am. Still we have frosts and freezing temps at nights. Tonights low will be 28F.

If you live near the coast, artichoke garlic planted now will likely finish okay. Inland the summer heat will likely fry it before it heads up decently, but as the previous poster pointed out it will still make stalks that are quite edible (and unavailable at the grocers). The stalks and young bulbs are milder in flavor than mature bulbs.

Some of the nurseries here carry garlic plants this time of year. You can use the started plants for this year and then when you harvest your 2010 crop later this summer you can re-plant some of your harvested cloves in the fall and perpetuate your crop to 2011. You can add another variety or two this fall for the following year. I love growing garlic because it grows through the winter when not much else is and it is delicious! This year's varieties: Music, Nootka, Red Tochliavri, Early Italian and Early California Select. Shallots are cool too.