As has been said, everyone has their favorite car rental company; look at the sponsors here, and send an email asking about rates, as their posted rates aren't always accurate. There are taxis, but no Uber. From GCBC, which I highly recommend, you can walk to any of the restaurants in Grand Case for dinner, and there are several nice beach restaurants further down the boulevard, which is walkable if you're so inclined, although a little farther. I recommend Le Temps de Cerices, and Captain Frenchy. The beach at GCBC is also lovely, as is the restaurant there. Hotel guests get priority on beach chairs, and there are also chairs on the grassy areas in front of the hotel rooms.