Really nice large lot.

Your yard looks good as is -- but then I like an uncluttered look and prefer the yard to be uncluttered when mowing. One exception is a bird bath -- a plain concrete one would do. You can leave them unpainted or paint the outside any color you want..

http://www.allbirdcage.com/wp-content/uploads/2015/12/bird-bath-concrete.jpg

Something you might consider for your side yard is a patio -- there seems to be a trend of putting them in the front now. More patio equals less grass.

http://c0263062.cdn.cloudfiles.rackspacecloud.com/content/images/sized/front-yard-patio-ideas-visual-sameness_086e0058d8297bf2ae78c70aebe1197f_3x2_jpg_570x380_q85.jpg

You might consider a planting area or hedge in front of the dark fence between your yard and your neighbor's yard to brighten up that corner a bit.

Some flowering shrubs by the side of the house could be a plus, especially if camellia or other flowering bushes would grow where you live. Ditto in front of the siding on the right front of your home. With children playing in the yard, cacti might not be a good idea.

Some vines are drought tolerant and you might consider an arbor with vines above and stone or brick patio below.

A word of caution: Any "garden" of any size takes some work. Having no plantings look better than having poorly kept ones so don't create more work for yourself than you have time to do.

Separate your yard from the neighbor's with a fence. Ask if they would be interested in sharing the cost with you...they also might be interested in a separation if you can agree on material and height. Reduce the size of the lawn by taking part of it out (roots and all) and replace it with an area of low-water plantings and mulch. Bird of Paradise, Russian Sage, day lilies, agapanthus, roses and Indian Hawthorne (aka raphiolepis) are among the perennials which don't need much water once established in California. They also require little maintenance. My CA yard is in full sun almost all day and these do well.

Hi..saw that this came up even tho you posted a while ago. I'm betting you are in norcal..maybe.. cause those slopes look real green. There are alot of groundcover that is drought tolerant but still looks green. When people tell me no arizona style below are two pics of groundcover I use. You may want to find a landscape designer in your area to help you.