I don't think those plants take well to pruning...they clump up from the base, and so there isn't really a way to keep them looking small. They will continue to spread outward even if you keep them short, and eventually you end up with something like this in just a few years:
http://www.public.asu.edu/~camartin/plants/Plant html files/Hesperaloe funifera sheared.JPG
I wouldn't put those there.
If you are growing citrus you must not get too terribly cold. There aren't that many things that will thrive with no supplemental water at all, but with a little help (every other week maybe) your options open up a lot!
What kind of look are you going for? tropical, deserty, somewhere in between? Vines, succulents, flowers? No spines allowed, or are they OK? I see you had some cacti back there before, but they're gone now. They can be a little tough on inflatable pool toys! Just trying to get an idea of what you might like.
Of the stuff we've put in, here are a few favorites of mine for Tucson:
Yucca recurvifolia (weeping yucca, huge stalks of white flowers)
Salvia greggii (lots of colors available)
pomegranates
Pedilanthus macrocarpus
Poliomintha maderensis
Lateveria maritima 'bicolor'
Aloe ferox (all the aloes will need protection in low 20s)
Aloe karasbergensis
Aloe wickensii
Aloe variegata
Aloe hemmingii
Aloe vera
Buddleia davidii (butterfly bush)
lavendar (various types)
Hibiscus coccineus
smaller Hesperaloes (parviflora various colors, campanulata)
Drosanthemum floribundum
Chaemerops humilis (Mediterranean fan palm, looks like you've already got one!
Callistemon citrinus 'Little John' (fantastic low shrubs)
Caesalpinia gilliesii
Urginea maritima (winter growing bulb)
Eremophila glabra ("emu bush" once was hard to find, now getting easy)
Agave (my favorites....)
- victoriae-reginae
- titanota (protection below 30)
- 'Sharkshin'
- pelona (very very drought tolerant)
- parryi
- montana
- lophantha 'Quadricolor'
- ferdinandi-regis
- bracteosa
- parrasana
- 'Little Shark'
Wow, that got really long really fast.
- - - Updated - - -
Oh, forgot the vines.
Hardenbergia violacea 'Happy Wanderer'
Parthenocissus 'Hacienda Creeper'
Jasmine
The idea behind it came from eliminating the plastic pool drain and joining the slate and travertine decks. I think it turned out quite well (better once the slate gets sealed)! Onto the next phase - we decided to stucco the back fence and paint the house since it looks like junk next to our shiny new pool! Landscaping is on hold until we can find the time to finish that up. 
