Can I negotiate at the dealership if I'm paying cash?

Yes. Paying cash doesn't prevent negotiation, but it may affect some offers, because certain advertised discounts are tied to dealer financing. Focus on the out-the-door price rather than the monthly payment, and ask whether any rebates require financing. If the dealer offers a better rate with a financing-tied incentive, you can compare the total cost. Make sure you understand any prepayment rules if you plan to finance and then pay off early.