Yes – you can book a rental car for pick up at one location, and return it to a separate location of the same car company on the same island if there is more than one location on that island. The Big Island is a good example, as many people pick up their rental cars in Kona, and return to Hilo as they fly into Kona and leave from Hilo. There is often a drop charge for returning to a different location, and that drop charge will show in the total when you choose a drop location different from the pick-up location.