I generally buy fabric only when it's on sale. I usually buy for my stash, not for a specific project. When I started quilting I visited JoAnn's frequently, but now I find I can get better fabric at lower prices online or at sales.
This site has Red Rooster fabrics at $2.99/yard, and shipping is very reasonable if you buy enough to fill a USPS priority mail box. Their customer service is great!
http://stores.ebay.com/CROWSNESTQUIL..._sopZ10QQ_vcZ1