No it can't. It may encourage the salesman to work harder at a lower interest rate. All a downpayment does is put money in the salesmans pocket. Interest rates are dependant solely on your credit, downpayments go straight to sales. This is all on the preminition that you are financed through some sort of firm (bank, manufacterer financing, etc...) and not the dealer itself.
On topic, i would consider going slightly newer. i got my 05 jetta used (22k) from honda marysville with 0$ down and a crappy credit score, however my interest rate is raping me as we speak. The only money i had to put down was to balance the price of the car 15,xxx and what honda financing would give me, i think i was 700ish short i told the finance manager all i could throw down was 300 (which was kinda true, thats all i WANTED to put down) so he lowered the price of the car. At no point in time did we even talk about a downpayment.
Most of the car's you listed are pretty expensive, you sure you want to dedicate that much income towards something thats not a neccessity when you could just buy a cheaper car? being that your an employee of saturn dont you get some sort of discount?