Repeating what was said above...heh..
Prehistoric Pets in Fountain Valley is fun...but not the most helpful and yeah, wouldn't buy an animal there. They also have a location in Chino...now called Reptile Guru...alot smaller, but a bit better, I think.
There is Radical Reptiles in Stanton (near Cypress and Buena Park) in Hobby City. That is where I got my first corn from. I like that place...they're extremely helpful and let me play with everything.
I hear the best things though about Amazon pets...they have a location out in Montclair and a new one in Covina. Healthy animals, helpful staff.
Of course, if it's just feeders you're looking for, you can find that anywhere. I buy F/T mice from three different random petstores all within 5 miles of my house (I'm in Burbank). There's no need to drive 30+ miles just for feeders.
And the show in September is fantastic! Best show of the year, in my opinion...blows the others out of the water.