I'm no expert but I believe they grow mostly softneck varieties in California and other warm locals. Hardneck grows much better in colder climates where freezing occurs.
Both softneck and hardneck can be grown in colder climates.
As far as a dormancy period for garlic, I think you need a minimum of 6-8 weeks, someone correct me if I'm wrong. As I'm on the southern lake shore of Lake Erie, the dormancy period isn't a problem for me, unfortunately
. Boy, this has been a long winter, snow is falling as I write this.
You can plant garlic in the spring but it probably won't produce cloves, only what's called a "round", a single large clove. Hardneck garlic planted in the fall will start producing cloves in late May or early June, and harvest is around the 4th of July.
My preference is for hardneck garlic, each head produces about 6-8 large cloves, depending on the variety. Much easier to clean and work with when cooking, no little, rinky, dinky cloves to try to handle.