Call the Avis hotline and they'll find a location where you can make the swap. This happened to me after I received a Ford Mustang with a speed limit and volume limit set on the car. I rented at SAN and since it is a corporate location, they had to find another corporate location for me to make an exchange. I was assured that there would not be a fee, and this would simply be like dropping off and picking up any other rental.

One thing though is that my issue was partly their fault as they rented a car they shouldn't have. If you're uncomfortable, they may not be as inclined to switch you out. It's worth a call, but YMMV.