Okay here's my little run-down of the area. I'm in Orange County and most of my buddies live or work in the Inland Empire because it is so much cheaper to live there than it is in Orange County. Chino Hills is a fairly nice area, as well as Yorba Linda, but Yorba Linda is more of a family place with few apartments. Halfway between Riverside and the beach is Tustin, which would make your commute to Riverside on the 55/91 against traffic to and from work, which is awesome. Tustin/Santa Ana/Orange are areas that are being rehabilitated because more people want to live here and are willing to pay good money, so you can find an apartment for a decent price, but you're not in a fantastic area as of yet. I don't think I would want to live further inland in San Bernardino County because it is so freakin hot out there, but I wouldn't mind working there and commuting against traffic. My boyfriend lives in Huntington Beach (2 bedroom 1 bath off PCH $1500) and commutes to Chino and his drive is twice as long as mine, but takes half the time. I go from Fullerton (near CSF, 2 bedroom 1 bath $900) to Newport and it is the pitts.
In my opinion, if you're going to pay an incredibly high amount of money to live in CA, you might as well live by one of it's greatest assetts- THE BEACH. Huntington and Newport have an amazing nightlife and the scenery is not half bad. I would highly avoid Westminster because it only reachable by the 22 freeway, which is under construction for Lord knows how much longer and is down to 2 lanes. Or if you're more of a mountain person, something more towards Redlands would put you near the base of the San Bernardino mountains, but the smog is awful there. Avoid Fontana like the plague- it's called "Fontucky" for a reason. I could go on, but I really don't want more people coming here, so I'll quit the quasi-sales pitch. Good luck on your search!!
-Heather in OC