There is some BLM land about 2.5 miles off of highway 74 in Perris (located between the 15 and 215 freeways), but keep in mind you do need an off road capable vehicle to get there!
When you do make it out there it is a fantastic area to shoot at with room for medium range (200 yards) rifle practice. But it's perfect for pistol, shotgun, trap, skeet, and .22 fun.
It does get crowded over the weekends so leave early to beat the crowds (and the heat). if you do go out there be sure to clean up after yourself.
I'll post pictures and a map later tonight.