Are my student loans going to affect the interest rate I get with a Car loan?

Ok, So my husband and I are going to buy a car in august. We dont know when because the dealer doesnt have any on the lot right now but they are getting the car i want "sometime" in august. The problem is that I really need to be taking applying for my GradPlus loan right now but I am worried that it is going to affect the interest rate we get for our car loan. Also, my husband is the one with all the income because i am getting ready to go back to school full time so should he be the signer for the auto loan and me the co-signer, or should it be the other way around? Our credit scores are both great it is just that I dont have any income and I am getting ready to take out student loans in my name only. someone with loan knowledge help!