Maybe you have found something since posting this, but I used to live in Joshua Tree so am familiar with the area, but moved away two years ago. It looks like Riverside County is doing some work (possibly with the 4CA Campaign as well). Here are a few links:
https://pacesconnection.crowdstack.io...fornia-county-groups (Riverside has an email of someone to contact)
https://pacesconnection.crowdstack.io...Profile_2018_PDF.pdf
Good luck!