I want to address wildflower beds... including what to expect, what is necessary to keep them looking great, and an idea of resources necessary to keep these gardens spectacular.
Most wildflowers that grow naturally in Southern California sprout with natural winter water and are at their peak in late winter and spring per the amount and timing of rain. Most naturally occurring wildflowers that produce spectacular shows are of annual nature which means they sprout, flower, drop their seed and leave the seed for next year's germination. There are also perennial wildflowers that can survive throughout the year. In nature they usually die or go dormant when water is not sufficient.
For 20 years we were a hydro-seeding contractor for local landscapers, builders, developers and cities. Most of the wildflower gardens we planted were for temporary use to help with soil erosion or dust control during construction or after fire or other landscape issues.
It is our experience that the garden is at its best the first season for the annual flowers and the perennials will usually not bloom until the second year. For wildflower gardens that last longer the annual flower production becomes less and less each season for several reasons. Mostly that the ground where the seeds lie is occupied by other plants and weeds thus crowding out the annuals or not allowing them to germinate and grow. There also has to be considerable water put on the new seeds whether from the original seed mix or from the regeneration of the seed from the prior seasons seed drop.
Weed control and weed identification are paramount in maintenance of the Garden. Basically a lot of the wildflowers would be considered weeds in a manicured landscape. So we are basically planting desirable weeds. Chemical weed control is almost impossible in these gardens though we employ a wiper method when appropriate (where the herbicide is wiped on the undesirable plant to better and more permanently eliminate it)
The amount of time removing weeds and the quality and accuracy of the elimination is all important to aesthetics and the durability of the garden. Also, new seed should be installed on a regular basis. These of course should be part of a cost/benefits analysis and discussion.
For the garden to be blooming throughout the year is another situation. Balancing the water needs of new seed and not over-watering the existing plants can be tricky. Basically in Southern California trying to have a wildflower garden throughout the year is not natural to our climate and flora (though most of our landscapes are not natural to this area either).
Another idea is to plant natives and succulent gardens. With thought, consideration, and imagination we can plant some interesting gardens. I doubt if they will put on as spectacular a show as the new wildflower gardens are in spring when they are at their peak but they will be more enduring and will be much more California friendly and use far less water. Of course there is expense involved in this and I understand that the areas used for these gardens are scheduled for future construction.