Scotty is bang on, but just to add:
You cannot put a deposit down on a car that hasn't been announced nor a price confirmed.
Some dealers may offer to take a deposit from you. This means nothing as the agreement wil be between you and the dealer, not between you and Ford - meaning that you are on no official waiting list and if the dealer doesn't get allocated any cars, you won't get one.
The best thing to do is register your interest on the Ford website here:
http://www.fiestasportseries.com as the more hits/responses they get will go further to justify the cars creation.