A slang phrase from the Southwestern United States, indicating a person is more image or projection than actual substance.
It is probably derived from the region's contempt for people who are not cowboys or ranchers but who try to mimic the frontiersman image through superficial adoption of the region's folkways.
President Bush's new tax plan is supposed to help the struggling middle class and revitalize the stock market. However, closer analysis reveals that he's just all hat and no cattle.
This is a saying (and I can't for the life of me find the origins) that means that someone is all talk and no action/substance. Someone who dresses nicely but doesn't really have any money.
Joe says he makes a lot of money and wants to buy my business, but after checking his credit references I've found that he's all hat and no cattle.