I wouldn't bother with the site. The inventory online and in the store are quite different. Do sign up for their mailing list. You'll get coupons to print out sent to your email address and also sign up for the one to be mailed to your home. If you are a reseller or non-profit you can also sign up for their card which entitles you to an additional 10% off.
I completely disagree with the opinions on the quality of the fabric. I am a professional veil maker and do purchase a lot of my lace there - but ONLY with a coupon. (Retail is a dirty word in this house!) I've gotten lots of gorgeous Indonesian batiks, silks, prints of all sorts, and I purchase my machine embroidery stabilizer there by the bolt. Look for their red dot section - fabrics marked down 50%. I shop at several Joann's because their inventory is different at each -- even though two of them are quite far away. It was well worth the trip. I filled the trunk of my car with absolutely adorable prints which I'll use for making fun summertime aprons for resale -- for under $100!
I also shop in the home decorating section for heavy natural cotton which is great for making tea towels and aprons.
The only way to know if Joann's is for you is to go there and take a look.