We never rent a car, in part because we don't like the anxiety of worrying that the police may shake us down. I know that lots of people rent cars and have no issues, but I have just heard too many stories at the pool or bar to want to deal with it. In my opinion there is plenty to do near Playa Grande that you can either walk to or reach with a short taxi ride. But if you plan to only walk, you have to be able to walk a distance up hill on the return home to Playa Grande