Well, SoCal is kinda boring, really very little ever going on here.
See this?
https://coachellavalley.com/memorial-day-events/I'd rent a bike, and ride the wheels off it. Plenty of great roads in the region.
J-Tree is kind of a throw from beaches - not sure what gear you'd have when here, but least cost is probably the state beach camprgrounds. A few things: Not the best beach time of the year; tends to be overcast, it's a holiday weekend (!), and the ocean temps are still relatively cold.
There's a racetrack nearby ... I believe the good folks from Moto Forza are hosting a trackday on the 27th (Monday)
Keep us posted on your plans - maybe can connect for a beer or something if in the area.