thanks so much for the info @MrMiyagi

Tropical based:
https://steamproxy.com/sharedfiles/filedetails/?id=846355576&searchtext=owl (los angeles, that's pretty close :D )
https://steamproxy.com/sharedfiles/filedetails/?id=1133680320&searchtext=owl
https://steamproxy.com/sharedfiles/filedetails/?id=677044827&searchtext=owl

temperate based:
https://steamproxy.com/sharedfiles/filedetails/?id=719724415&searchtext=temperate
https://steamproxy.com/sharedfiles/filedetails/?id=925340750
https://steamproxy.com/sharedfiles/filedetails/?id=1200521995
https://steamproxy.com/sharedfiles/filedetails/?id=868109725&searchtext=australia

Find yourself a remote natural place on the coast to check out the water and also because you'll often see different vegetation, sometimes the most native vegetation. San Diego's really different, this is super dry https://www.google.de/maps/@32.6679352,-117.243549,3a,60y,181.26h,84.21t/data=!3m6!1e1!3m4!1sr4A4TEc21zSgmCmkQpj2jQ!2e0!7i13312!8i6656!5m1!1e4
OWL's gonna be your guy for map themes, he loves that So Cal coast. Some map themes that match closely (continued)

Here's the ideas you asked for on making your San Diego map realistic. I went to Google maps satellite view and found an area that shows some natural vegetation (usually a state park or side of the highway without houses nearby). I then match up the grasses, rock, and trees with trees and themes on the workshop. Example, I found this spot: https://www.google.de/maps/@32.7593543,-117.1896723,3a,75y,276.43h,93.6t/data=!3m6!1e1!3m4!1sxij_sviNyPdYi8ImgyOxyA!2e0!7i13312!8i6656!5m1!1e4
The grass is somewhat dry, the trees have a more white bark... looks like all of Pdelmo and Mr Maison's Australian trees, so go shopping for trees there. There are also several map themes that have dry grass color to match, Pdelmo and OWL come to mind.