Geothermal cooling works great as long as it is done right. Do it wrong and all you get is headaches, from the heat.

There are numerous schools, offices and houses in St George Utah with geothermal cooling. Most of these have vertical loops.
I doubt that you could bury pipe at 5' deep and do much cooling in your area.
A drip system to keep the soil moist is also a good idea since dry soil has very little thermal conductivity.

A DX geothermal system buried 6'-8' deep in your area would work fine. Also, the dry soil is not necessarily a problem. For DX, you just need to know the mean ground temperature. A soaker hose would be installed, but only needed to be used on the initial settling of the loop. It's run for 24 hours to compact/tightly fit the soil to the copper ground loop. After that, it never needs to be soaked again. It works wonderfully.

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