I am also a size 16 and you will have difficulty at Ann Taylor. I get a double whammy since I'm also tall with long legs. Ann Taylor sometimes carries a 16 but not always and the selection is limited. I have better luck with Eileen Fisher. Macy's tends to have a very good "woman's" (god I hate that term) department for size 16's and 14W's which has some designer wear as well.

Lands' End does carry up to 16 and I find it fits but but agree that LL Bean is better quality