Nancy, I belatedly realized I should have provided more context...as relatively few Californians are familiar with their local plant names, thus it's unreasonable to expect those much further afield would be!

So, here's the context...

A number of current BugGuide posts for Closterocoris amoenus appear on Salvia ("true sages" in the mint family, Lamiaceae), suggesting a possible host plant relationship. And I'm thinking the relatively new foliage in your post here resembles that of S. mellifera. For instance, compare your two photos with this image of new growth in S. mellifera (photographed by BugGuide's own Hartmut Wisch :-)...or closer yet this image.

Shrubby Salvia are a common constituent of the chaparral around Lake Miramar...and my hunch is the most likely candidates for the plant in your photos are (in decreasing order):

  Salvia mellifera: CalPhotos   iNaturalist
  Salvia clevelandii: CalPhotos   iNaturalist
  Salvia leucophylla: CalPhotos   iNaturalist

So, although it was a few years back, I'm hoping some of the images linked to above may resonate with your memory of the plant on which you photographed the Closterocoris amoenus nymph here. Perhaps a long-shot, but figured worth a try?   Thanks! :-)

.

...wish I had seen it as an adult - looks close to molting here.