If you're talking about conventional fossil fuel desalination, I invite you to do the energy audit on that activity. If you're talking about solar desalination in industrially-manufactured greenhouses, I invite you to do the energy audit on that activity. Don't forget to account for the energy-opportunity cost of land use.
I know there's a lot of hype surrounding desalination here, but a centralized energy-sucking plant (owned by the ultra rich naturally) is a counterproductive business-as-usual non-solution.
We can get a net-positive energy audit by redesigning our agricultural and storm water management. Right now they're designed with exactly the wrong goal in mind — shunt rainwater to the ocean in big straight hardware as fast as possible. This maximizes runoff instead of infiltration, so we're simultaneously preventing aquifer recharge and necessitating aquifer pumping by drying out the soil.
"Keyline" design—a method of cheaply altering landform to soak water—is probably a good start for these new infiltration maximizing strategies, but this is by no means a solved problem.
In California, like any desert, the name of the game is minimizing evaporation. This means all of the above, plus shading (e.g. date palms), sunken beds, buried drip irrigation, and dew/rain harvesting strategies like land imprinting.
Proper rainwater management is the lazy hacker's desalination. :D