Some of the new developements in your area at about your elevation are using native plants for this purpose. Plants such as Ilima with yellow flowers and Nio papa are used as ground cover and are available from the Home Depot and the nursury between Home Depot and Costco. Native accent plants that have low water needs are available in your area.

A good sourc of plants for dry or xenoscopic planting is available from the water company on Oahu via internet.

Pa'u o Hi'iaka is also be a good choice for a ground cover ... it takes some watering to get started but does well once it's established. Has small, blue-white flowers, very attractive.

For trees, kou is usually a winner at that elevation, as is wiliwili.

Here is a link that might be useful: Pa'u o Hi'iaka