raised-bed Raised beds in hot, dry climates.

I have two places to put a raised bed, one is bigger but without a drip-irrigation system, and the other has the system, but is smaller. I'd obviously like to make a bigger one, but I'm worried about them getting enough water. My family goes on a lot of 2-3 day vacations, and maybe one or two longer ones. Would I have to worry about neighbors helping me, or would they last a couple days? If it matters I will be using 40% shade cloth too
They should easily last 3 days if you water them a lot before you leave, assuming the raised bed is over ground soil so the roots get down where the soil doesn't dry out very fast, so you can give them a lot of water at once without it resulting in soggy root rot.  I'd think you should be able to go at least a week, but I'm not in AZ.
As for which to choose that could have a lot to do with how wiling you are to spend the extra time watering for a higher yield.
If you can get them from the local tree trimming companies than they are usually free.  If not you can get them bagged from a home improvement store, get shredded hardwood mulch.  Mix some into your soil but mostly topdress with a good couple inches.
Problem with desert grows--------there is a fine line between too much water and dead, dry pepper plants.
After 3 years, I may have it figured out for next spring.
This summer I went on a 2 week vacation, all the yard and garden are on timers for watering.
It rained for a week while I was gone. :tear:
Ive been reading a few really good papers on the benefits of RCW in ALL types of soils.  Its been successfully utilized even in the desert.