Corona is a pretty nice place. Downtown sucks, but what downtown doesn't? But even downtown has it's finer points, like "Annie Get Your Gun" Gun shop.
I heard that Corona is getting all of the gang bangers from LA moving there due to the cheap housing. What I know about Corona I remember from a quick drive-through about five years ago (I stopped at a Safeway there). I'm sure there are some nice sections there however, as it is a pretty big place.