The combined rates you received are very good.
Re Hertz location in MIA. It is not far from the terminal. However, when you drop off the vehicle, make sure you get computerized driving direction (i like maps.google.com). It seems that construction is alway going on near that part of the airport. The area where Hertz is located seems a bit run-down. Use caution as always, particularly if you return the car at night.