Hi Edie, Kimberly here from landscape-solutions-for-you.
Thank you for asking the question on your hillside and what to plant. With any landscape project one of the critical steps is to prepare your soil. If tilling isn't feasible, use manual tools to prepare your soil. Jute is a fantastic commercial landscape fabric that is used on hillsides and will help against erosion. You can purchase the Jute at most landscape supply stores.
Once the prep work is done and Jute is put down, you are open to plant a variety of specimens on a slope. Check out the tropic section on this site as there are many of these plants that will do well in your zone as well as on a hillside. Also, if you haven't looked at the simple solutions section, there is a page on slope planting with evergreens. I will link you to that page from here.
If you still need more specific plant names, feel free to reply here or on the contact form. The best of luck to you and thanks again for asking the question. Hope you are having a great day.
Kimberly