Jan's Tropical Fish on the south east corner of Central & Moreno in Montclair. Take the 10 FWY, Get off on Central, it is a right, and then a right into the shopping center. It is toward the Fallas Apparel across from Petco & Harbor Freight. They have FW and SW, and their layout is well designed. They don't have a tremendous selection of exotics, but their livestock is generally very good, and the markup vs Orange County stores is only about 10 to 15%, so for just a few items you save money vs the drive to OC. They carry a good selection of the Reef Nutrition line of products, which is handy if you ever need some of those, and they have an amazing stock of general dry goods.
Rancho Tropical Reef on Foothill in Rancho Cucamonga/Ontario is also pretty good. It is off the 10/15 Fwy. Take the Foothill exit, and head west, and it is on the North (right) side of the street about 2 or 3 blocks as you pass Victoria Gardens (big shopping center you'll probably spend a bit of time at, living in that part of Inland Empire). He has alot of Softies and some LPS, and focuses on easier to care for fish. he'll have Target Gobies, occasionally Mandarins, and some blennies, and clownfish galore. He is a generally nice guy, but try not to get too many opinions in. His stock is good, but his advice can feel a little bit threatening at times (he insists that his RO water is the cleanest in southern california, and might provoke an argument if you say you've found an RO dispenser that is just fine). He has some great deals on frags. If you buy 3 of the 10 dollar frags, you get 1 frag free. If you buy 2 of the 20 dollar frags, you get one free, and there is some sort of delineation from there. If he is in a good mood, he'll occasionally "slip" a 20 dollar frag into the 10 dollar frag rack for you.
Some people like Mystic Reef in North West Riverside. I've never been there, but it is only about a 15 minute drive from Ontario.
There is also Fontana Tropical fish that has some interesting specimens, but the only time I went in there, I counted some dead fish in their display tanks, which is always a little uncomfortable for me.
The best places, you need to drive down the 57 or 15 Freeways, hop onto the 91 from there and branch out.
My personal favorite is Age of Aquariums in Long Beach/Signal Hill. It is a 150 mile round trip for me, but worth every penny of gas in savings alone. Their selection of SW and FW is simply amazing, and their display tanks are gargantuan.
Pet Supreme in Sylmar is good, but it is an even further drive, in most cases, than AoA, which is still superior. Pet Supreme is an amazing general pets store that is independent, and has a humungous frag rack in the back. Their SW selection of fish isn't too great, and the prices on everything is not too fantastic, but if there is a particular type of coral you are interested in, you can usually find it there and in very good health.