Check out the forest service website (Angeles, Los Padres, etc) for target shooting. You can call an appropriate ranger station for more info and conditions, this is what I normally do before I head out. Angeles Forest only has a couple pay to shoot areas, but I'm not familiar. San Bernardino NF has a few areas where you can do some shooting and off-roading. Bee Canyon is my go to. I went through Bee Canyon on Saturday and it's pretty tore up from the rains. The road is washed out in a couple places so high clearance is a must for the time being. I made it through in a stock trail, but not without hanging a wheel.
Bring trash bags and please clean up after yourself though. We don't need to give people a reason to shut these areas down. I usually pack out more than I bring.