Check every day. Different things will go on sale at different times and at different rates. It doesn't all happen at once. Unless you're the only quilter in town, don't gamble by waiting too long for the really good stuff to hit 50% off or more. Unless you're standing right there when they mark it down, it could be gone before you get there.
Can you tell our local WM fabric department downsized? I checked every couple days until they were done. I think I have more of the fabric now than they do. (And, believe it or not there are colors, shades and values I STILL need! LOL)
I don't know how it'll be in yours, but in ours there aren't any more distinct "on sale" tables. Just whatever they don't feel like putting on the racks mixed in with the $1 stuff and the marked down stuff.