Landscaping works that if you go to a garden center to pick plants they may... help if you bring in some pictures because you are buying the plants from them and the design fee is covered in the plants. But they only sell you the plants they have which often gives you a limited palette.

Often if you have a design/build gardener they will charge you a design fee but your plants will cost less. So actually hiring a designer or going to the garden center evens out. Are you going to be installing it yourself? Have you tried digging in our southern CA soil? It's often very compacted and you also will need some sort of irrigation system.

A good way to start is by browsing houzz professionals in your area and seeing if you like any of their designs .. add them to your ideabook and you have a start. I'm located in southern CA and have done hundreds of residential designs and can help you with some quick ideas and getting you the plants. You'll find the less headache and the price is quite compatible to your budget.