I grew up in San Bernardino (AKA: the arm pit of SoCal) I used to drive quite a bit between SB and Sacto when I was in the USAF. Now I live in Redlands and you will be passing right by my house (look for the Wabash exit).
IMO from the 10 your best and fastest route to get to the 99 and ultimately Fresno (and also bypass the LA traffic) is to take the 30 (we call it the cross town freeway) its only 10 miles long, but again, you bypass the 215/10 interchange. The 30 ends at the 215 and you take it north until it merges with the 15 in the Cajon Pass. Now here is where I would differ. I would take the 138 west, which is about half way up the Cajon Pass. The 138 ends up in Palmdale connecting with the 14. You take the 14 north to the 58 west and then the 99 north. This route shaves 45 minutes to hour off the 395 route.