Lantana can get leggy and need to be cut back every few years is what I have read and will turn black if frosted. Some of mine is already black.
I would suggest myoporum. I have it the pink and really like it. It also comes in tiny white flowers and my city has it everywhere.
Here's a pic I took today of a robin near the myoporum.

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You are being smart to question using Festuca ovina as a mass ground cover if you don't want to have to divide and replant, and it is much easier to maintain if it is used as an accent rather than a mass planting. The recommendation for the Dwarf Myoporum parvifolium 'Dwarf Pink Form' is also one that I would second, as I use this a lot for mass plantings, and it performs well while not demanding much care, and needs no pruning and grows densely enough to suppress weeds. Another thought, if you were looking for the gray foliage color might be to mass plant Graptopetalum paraguayense, which is also extremely easy to grow, drought tolerant and hardy. Other low growing and easy ground covers for full sun might include Teucrium cossonii, dwarf forms of Lavandula angustifolia, Convolvulus mauritanicus, to name just a few. Something completely different in appearance, but also surprisingly drought tolerant, might use Setcreasia pallida, for a mass of brilliant purple foliage color, or Senecio mandraliscae for brilliant blue foliage.

Various ornamental and edible thymes work well with full sun and don't need a ton of water.

I like the bright green of the myoporum, and it has pretty, ferny looking foliage.

Lantana builds up a thick dead thatch underneath a thin layer of live growth. The dead stuff gets thicker and thicker. Not good.

Will there be irrigation? Besides the above suggestions, prostrate rosemary is nice and no-care for several years (then rip out and replace). Perhaps a groundcover Ceanothus or two? (you might be too far inland). Here the Senecio mandraliscae is beautiful but it does need some summer water else I get dead spots. Santolina chamaecyparissus nana if you don't mind deadheading/shearing once a year.

My front yard has a south-facing slope. I had Baccharis and one Bouganvillia on there for 10 years. It had become a terrible nesting ground for rabbits. We were overrun. Now I'm replacing it all, leaving the Bouganvillia and adding Aloes, Agaves, Dyckias, Dudleyas, Senecios, Yuccas, Calandrinia grandiflora, etc. The bottom edge is a band of Dymondia margaretae which is effective at preventing runoff (dense roots).

One fabulous south-facing slope I saw was just a sea of Senecio madralescae studded with Agave 'Blue Glow'. Wow was that sweet!

Ditto on the Myoporum parvifolium.. I used white myoporum in my front yard on a south facing slope and it's filled in perfectly. I don't know how to post a picture, but it looks a lot like goblue's does.

Thank you all for these suggestions. Truth be told, I feel overwhelmed with the choices. I've planted highly-praised plants before, thinking they were in the right soil/sun/shade situation, and they didn't work out for whatever reason. I did some research on the Myoporum parvifolium recommended above and found 1-2 sites that said it can get woody underneath, just as Lantana is prone to do.

We're meeting the landscape designer at the nursery tomorrow. I feel like spinning a wheel and picking whatever it lands on. I'm taking my new Sunset Western Garden book with me for reference.

I think the Myoporum takes a lot longer to get woody underneath than Lantana, and doesn't build up such a thick layer of woodiness. The big slope on the other side of the park has Myoporum that is somewhat woody, but it's been there since 1980.

Thank you. It's not a big area... maybe 8x8', and it's "down in front" near the sidewalk, very visible to passersby.

I researched the Ceanothus groundcovers in the Sunset book and didn't see one that meets all the requirements (size, zone, etc.).

I have Myoporum in Pink and White, it has been on the hill for 6 years. It gets very woody and every year or so I get a section that will just die. It is easy to grow cuttings and replant the sections. I have planted Lantana also on the hill and it gets big but not too woody, it also goes dormant or dies with extended frost. I would love to find something that does well on my hill in Ventura County. The only thing that grows with no abandon is the stupid mexican primrose that the builders seeded the hill with. I can't kill that stuff.