If you can imagine being in the mountains in the SW. In the Big Bend of TX, up in the mountains, the Agave havardiana grows along with junipers, pinyon pines, oaks etc...You might try to emulate plantings such as this that can handle natural rainfall. Other spiny shrubs and small trees will keep the unwanted out too. Dasylirions work well along with Agaves , Yuccas etc. for a hedge to keep people out.

you didnt mention where you are---if you are in arizona the trees mentioned above (which are potentially excellent suggestions) are used to getting by with at least some normal summer rainfall if you are in the interior valleys of california (for example) you would generally not expect summer rainfall and might have to consider providing someadditional water for trees during the summer. of course all the plants will need regular irrigation for at least the first year or so during the dry season. the agaves may not be happy under evergreen trees especially those with dense crowns. you might consider some at least briefly deciduous desert trees like cercidium (palo verde) or porosopis (mesquite) which will provide light shade during the warm season while letting the sun in during the winter. their small leaves quickly dry up once they fall and should not mess up the agaves. the evegreen large shrub/small trees known as fremontidendron are very drought tolerant one established and have spectacular spring flowers and might make a striking screen. other evergreen trees to consider inclufe acacia stenophylla, cupressus arizonica ssp. glabra, cupressus forbesii, and possible brachychiton populinifolia (bottle tree), also the palms washingtonia filifera and robusta as well as brahea armata and finally ocotillo (fouquiria splendens) a large multi-stemmed cactus like plant with spiny stems and brilliant red flowers as another possible screen. hope this helps.

The Ponderosa pine needles are messy, but they don't phase this Agave americana.
Live oak, Black oak, Mimosa, and Acacia growing in the same vicinity. I think
you could plant some drought-tolerant, fairly low-mess Juniper species nearby.

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For a quick, evergreen screen with similar exposure as yours, I planted Acacia saligna. Works great.