I recommend to visitors rent the smallest car you can comfy fit into. The Kauai (or Maui etc) roads are narrow, the parking spaces even narrower and gasoline is close to $3.00/gal. As hinted you will see many non-HI lobster-colored people in convertables. Also the convertable cloth top is easily cut by thieves and your valuables are stolen and sold usually for drugs. I have seen many cut and robbed in Maui along the more remote spots.
MisterNice