Either way its always best to deal from a position of power. Get yourself pre-qualified before you walk into the dealer. Then, if they offer you a better promo rate, fine, but if not you don't need play finance games and all you have to discuss is the price of the car.
Think of buying the car and the financing as completely separate transactions and you'll never end up lost in smoke-and-mirrorsland.
This way you also don't have to swallow any BS about you don't qualify for this rate or that rate. As others have mentioned, its not in the dealer's best interest to offer you the best rate going whether its through a bank or through Ford.
Scott | 2012 GT Premium Coupe • Performance White • 6R80 • HID • 64M Wheels • Ford All-Weather Pony Mats & Trunk Liner • GT500/GT Rear Mud Flap Set • Ohio's Horses License Plate • Raxiom Aero Tails
If you love your dog, get a microchip, they really work! My lost dog was back home in just under 24 hours thanks to the good citizens who called the county and the microchip that told animal control exactly where he lived.