It is true about the guilds - but here's the rule - we only have to present our guild membership cards in order to get the JoAnn's card worth the 10% off. Also, if you belong to any other group that sews, you qualify.
If your local JoAnn's doesn't honor this easily, go up the chain of command and don't give up. They have this in place, and so must honor it. It's everywhere - nationally.