These are the least thirsty of all plants.  
Water while becoming established every 1-2 weeks for a year or two.   
Once established supplemental watering is not required, 
but plants will perform better with once a month deep watering.

Agave or century plant.  There are different varieties.  This one is quite large (base of plant is 6 feet )and dramatic when in bloom.  This plant will die after blooming, so it is important to plan ahead when using agaves.

Variegated agave grows to about 3 feet. 
Sends out offshoots which can be transplanted.

This is a traditional landscape design
adapted for the desert.  Afgan Pines with rock and gravel.

Prickly Pear comes in a variety of shapes, sizes and colors.
     
New plants are easily started by cutting a lobe and putting it in the ground. 
Water once a week until established.  Mulch with gravel and larger rocks close to base.

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Bear Grass,
a native grass

Agave grouped with other low water plants,
Chocolate Flower (yellow) and
butterfly bush (purple).  Mulched with gravel and rock