One to consider is: chitalpa tashkentensis.

Features include:

1. 20 feet maximum height

2. Fast grower

3. Drought tolerant

4. Beautiful, orchid-like flowers all summer

5. Non-invasive root system

6. Non-messy flowers, although the tree is deciduous.

I have had one of these for 4 years and have been very happy with it. It seems quite trouble free and the flowers are very attractive.

-Brett

A sugar maple would be well outside of its normal range and probably fail to thrive.

Palo Verde Desert Museum.

I also don't think the maple is a good choice for a hot CA garden. Here are some suggestions that thrive in the warmer areas of CA.

Bronze loquat, Eriobotrya deflexa, becomes a nice small tree, it's evergreen and the leaves are large and easy to rake up when they eventually fall. It isn't a super fast grower though. Bronze loquat is not the fruiting kind of loquat which is Eriobotrya japonica. Their abundant fruit can get messy but they are edible and somewhat faster growing than the bronze. They also make a nice small tree, both are suited to CA climates.

Arbutus 'Marina' also becomes a nice small tree. It has interesting bark, can be grown multi-trunked or standard. They are fast growing and have nice flowers but they also have fruit that might be messy depending on the area. I have a Marina in my garden and love it, I planted a 5 gallon in Nov 2014 and it is now more than 6 feet high.

A third very common small tree in CA is the Crepe Myrtle. They are deciduous but they have nice flowers in a wide variety of whites, reds, pinks and purples, interesting bark and thrive in the heat. They make a great focal point in a small garden. A nice thing about Crepe Myrtle for a beginning gardener is that they are common and easily found in nurseries and big box stores.

All trees have tradeoffs, you'll have to decide which characteristics are most important to you. For example I also have a PV Desert Museum and it has been a very fast grower and very drought tolerant, but I wouldn't call it a clean tree, it has very small leaves that continually fall, creating a kind of leaf dust throughout the year. I don't think they would be low maintenance in a small city garden. The tiny leaves also mean it doesn't create much shade which sounds like something you are looking for.

We have 2 chitalpas, one pink and one white. We liked the first one so much we planted a second one! The only issue we've had is aphids on one with new leaf growth in spring. Our loquat tree is pretty, but drops a lot of leaves pretty much all the time.

Lol someone wants a mythical tree. What a surprise.

Dang I was gonna suggest Crepe Myrtle. 4 on a pattern with seating would be cool. The crepe is an African tree. It seemed well suited to the described environment.

Crepe myrtle only if not near walkway, patio, driveway. I have 5 and the ones in the lawn are no problem but the one over the patio is messy especially this time of year when it drops buckets of purple flowers which track in the house. They catch in spider webs, cover the ground like mulch, hang in shrubs. All the bark falls off at one time of year, then in the fall, all the leaves. I do love the trees though, even the one on the patio, and the flower issue only lasts a month or so.

Actually they are only messy young. The full grown Crepes we have no longer have the curly birch style bark. Perhaps a sterile hybrid is called for, that has no flowers, but that is a mythical tree. They all have some drop.

Sure Hoang, a mythical tree doesn't exist. It's a fantasy. That's what your list of criteria is, a fantasy.

Tricky--I respectfully disagree. The tree on our patio is over 42 years old, still blooms heavily, sheds bark. Maybe we have different varieties or maybe the zones make a difference.

I think Tricky was being sarcatic, hence the reference to a mythical tree.

OP, the problem is that all trees shed leaves, even the evergreens, if they flower, they shed those, and, unless they are sterile like the Chitalpa or PV Desert Museum, they shed some sort of seed pod or fruit. If they flower, they also attract bees. Some of them are tidier than others, but none of them are perfect. It's a common post here from people who are looking for tidy, non-shedding, long-blooming, beeless plants which just don't exist.

Another, somewhat larger choice for you would be a fruitless, Swan Hill olive. That particular variety does not set any fruit at all. Maximum height is a little large for you, but they can be aggressively pruned by a professional to maintain whatever height you want. They can also be transplanted as really ancient trees (>100 years old!), so the size you plant is only limited by your budget. Besides, they are just so darn glamorous.

I don't think that crepe myrtle is particularly messy, but it may not be tall enough as a shade tree. We had one outside our kitchen door at our last house that didn't seem to shed that much.

@lgteacher thats socratic to you..but not really. I was just out raking and they are not as busy dropping as so many others in my yard. In the photo the crepes are on the right, watermelon color I believe, and not a bad height re what op was wanting. Its 5pm July 10 in the picture.

Yes, I retract my remark about the height of the crepe myrtle. The one in the backyard of my old house was poorly sited and really needed to be replaced. It only got a half day of sun and developed powdery mildew every year. There are some nice ones in bloom right now in my current neighborhood and they are a good height for a shade tree and quite handsome. I assume that the ones in the median near my house are a mildew resistant variety since we are closer to the ocean here.

We don't have a backyard. Just trees. And they drop heavy. We have forest

Where in California? 9b could be Sacramento to Riverside or even Palm Springs,Gilroy too.

If you are a soucal 9b is a huge difference then a central or norcal 9b.