Flat Sedums are a possible. Pebbles/rocks and bromelliads. Echeverias. Lampranthus. Carpobrotus. Arctotis. Gazania. Osteospermum. Trachelospermum kept clipped. Sanseviera.

I was once sitting on a park bench and realized that rats were running around in the 1' tall Vinca-type groundcover right next to me. Ugh. Anyway, I use lava rock in planting holes to keep voles from eating my daylily roots, so maybe adding a sprinkling of lava rock to the soil when you remove the myoporum would help keep the tunneling rodents at bay.

Thank you for the suggestions! We're going with grass(to fit in with the neighbors) on the street-side flat part. Still deciding about the slope. Want something cheap and easy since we're planning on a retaining wall eventually.