How about an arbutus unedo, or arbutus 'marina'? Both would do well in the valley.

I don't want the mess of dropping fruits and don't want to attract birds, rats or anything else.

If you have a tree, birds will occasionally sit on the branches, even if you have a plastic tree.

Yes, but I don't want to attract more than normal by making it a food source.

I think you're going to have to make compromises on some of your requirements. Nature is, well, nature.

Western Red Bud - cercis occidentalis, will produce tons of seed pods which will attract birds and insects that bore into the seed pods to eat the seeds. The insects will, in turn, attract birds. They are native here, which means they are a native food source for local wildlife.

Bronze loquat - Eriobotrya deflexa, produces fruit and is not drought tolerant

Purple Leaf Plum - Prunus cerasifera, produces plums, and is not very drought tolerant. Also drops leaves in winter.

Crepe Myrtle - lagerstromeria sp., some varieties produce sap (or maybe harbor sap producing insects, not sure which) and flowers will drop continuously in summer as they fade. My 90+ year-old tree is very messy. Also, these are not too drought tolerant. My neighbor's tree of similar age to mine died in last years' drought when they shut down their irrigation.

You could consider some arctostaphylos like Dr. Hurd, or , but you'd have to get rid of the lawn or you risk watering them do death.

My only other recommendations would be Chilopsis linearis, or Dodonaea viscosa 'Purpurea'. If not pruned to death, they will grow into lovely small trees very quickly. They're native to desert areas so they are very drought tolerant.

I have never seen fruit on a bronze loquat. I would say it is a pretty good tree that meets most of your requirements.

Bronze loquat (not the fruiting kind) makes a tidy small tree. Crape Myrtles are nice but you don't want to damage the base with the lawnmower to stimulate the growth of suckers at the base of the trunk. There are all kinds of sizes and colors. Purple leaf plums are lovely but don't live very long in SoCal--not sure if that is also true for NorCal.

Western Red Bud is messy and will ruin the lawn, filling the area completely with surface roots. Also they reseed everywhere and the seedlings are hard to pull. Been there, done that. I'm still pulling seedlings 5 years after getting rid of those blankety blank redbuds.

So, what about Crape Myrtle with a border around the trunk to protect it from lawnmowers?

Anything of any significant height whatsoever will fail to conform to two of your stated restrictions. You should be looking at shrubs, maybe something architectural that has a lot of visual impact for the amount of space it occupies.

Something like a clump of yuccas, to name just one example.

I like the redbud. I've seen them used in public plantings here. They do get worn looking by late summer. That could be they aren't watered enough though by the city.

I think I can narrow it down between bronze loquat and crape myrtle and maybe also consider purple leaf plum and just treat them to suppress fruiting.

Also consider a chitalpa tashkentensis: drought tolerant, beautiful flowers all summer long and doesn't make a mess. It is not super fast growing but you might have to prune it back every now and again.

My purple leafed plum is Prunus cerasifera 'Krauter Vesuvius'. It produces very little fruit--maybe 1-2 fruits per year for the entire tree. Be aware they are susceptible to a range of pests and diseases though, and not often considered long-lived.