Once you sign up they own you. They can move you from base to base or send you anyplace they want. This has been a huge problem for enlisted men and women trying to buy homes. They buy a house thinking they're gonna stay in that one place then get moved across the country and can't get out of their house payment. Just something to consider before you sign up. But yeh air force is good. Unless you're a pilot I would think there's probably less chance of being shot at than say the army or marines.
You can stay for a long time without being called up for service. You should join the Air Force Reserve as they offer good opportunities for training at no cost and more to offer competitive pay and benefits. The reserve offers full time as well as part time jobs, with the primary duty just being readiness. For more information, go to http://afreserve.com/?:Jobs and http://www.airforcereserve.com/.