My experience is that unless it is fabric from an actual quilt store, it won't sell priced more than $1 a yard. Some exceptions for specialty fabric.
Occasionally, a quilter purges fabric around here and usually prices it at $2 a yard (quilt shop fabric) and it goes. Be strict. If they try to bargain you down on the quilt shop fabric, just say no. Someone else will come along knowing what a bargain $2 a yard is.
I personally have found that non-quiltshop Christmas fabric is the hardest to sell at a garage sale. I don't know why - I've never been able to sell any, even at 50 cents a yard. However, if you have a LOT of fabric, be sure to list your sale on Craigslist and include photos of fabrics laid out. You will get a lot more fabric buying customers showing up.