California actually has what is probably the best highway signage of any state in which I have driven. Highway signs in California keep drivers aware of what highway they are on, what direction they are going, and how far it is to communities and route junctions down the road. In California, I don’t recall ever having gotten lost because of the lack of highway signs or trying to follow signs that were ambiguous, misleading or confusing.
In my experience, New Hampshire is the worst state for highway signage, followed by Maine, Pennsylvania, Texas and Nevada. States in which I have experienced good signage include Arizona, Colorado, Ohio, Vermont and Virginia.
Last time I was in CA, they had half of the light bulbs for the signs turned off, so you could barely read the most excellent signage while trying to negotiate the traffic that was poorly lit because half of the highway lights were turned off. It was a very frustrating and dangerous situation.