Maybe lazygardens will chime in. S/he (?) made some nice suggestions to a previous query. See below. I love blooms - and bees - so about the only moderate size trees I can think of are ornamental purple plum, Bradford pear (not sure about blooms on that one) or evergreens.

Here is a link that might be useful: suggestions for trees

The Chinese Pistache is nice for color, but it is deciduous, so you're going to have leaves in the fall to clear.

I love the look of the Chinese Pistachio. What about bees? I don't want to attract bees that could potentially harm a resident living in the community. I have attached a link that will show some pics of the community being built and the courtyard in the middle. Thanks for the info. I am going to keep researching. Any other thoughts...let me know. Thanks!

Here is a link that might be useful: The Summit AZ

The Chinese elm is nice too.

This is a very pretty tree, only partly deciduous in cold winters. If you're buying big box trees, you should have no problem with frost. Very young trees really suffer at freezing temps. The link below notes that the tree gets to 60' in height and eventual width. I have never seen one that big in Phoenix.

I love the Chinese Pistache and if you're so inclined, I would not be worrying about bees. There will surely be something in the garden that will attract bees and bees in trees are less likely to encounter humans that bees near the ground.

Here is a link that might be useful: Sissoo (Indian Rosewood)

There are lots of ways you can get color without getting it in the trees (especially if the owner doesn't want any flowers on the trees). Colorful planters, furniture, benches, umbrellas, shade canvas, walkways, half walls, colorful tile inlays or even a part of the courtyard where the residents can get involved by painting their own tiles that get used in a path or something. Succulents can give you a lot of color as well without a lot of litter.

The choices for "shouldn't drop "too many leaves or pods" is a question of whether they want the continual small dribble of leaves, pods and debris from an evergreen, the peaks and valleys of the leaf drop, pollen drop, pod drop, leaf drop of the mesquites ... or the once-a year leaf drop of an elm or ash.

Australian Willow (Giegera somethingorother) is a nice evergreen, very tidy, pretty bark.

Mexican ebony has lovely smooth patterned bark.

The sterile Desert Willows have the annual leaf drop, flower and drop blooms, but don't set seeds.

Colorful foliage ... the above-mentioned pistachio

Look for trees classed as "patio trees" in Sunset's Western Garden book.

LOL, lazy! There's no such thing as a totally tidy tree; something is always dropping. I used to think I wanted my very own pecan tree - till I saw the mess my neighbor's makes. OMG.

I love my chaste tree(s), but I didn't recommend one because if it's not pollen, it's sap, leaves or berries. No one has mentioned crape myrtle, so I will. There aren't may prettier small trees, but you'd have to get past the bee paranoia as they bloom profusely.

Actually, I think they're going to have a lot of problems having a garden if they want neither litter or bees. A rock garden, perhaps.

A Fig tree is not too messy. Get a good tasty variety, not something from Home Depot. Your residents and staff will love the fruit and it is not a messy tree. It stands up to pruning well.