This is from 2001 and they have continued to get worse since.
I couldn't find a recent assessment.
California Tops the List of Worst Roads in the Nation
http://www.allstays.com/Features/CaliforniaWorstRoads.htm
Dec. 27, 2001--California's rutted, cracked and neglected roads now rank at the bottom of all 50 states in roadway quality and per capita dollars being spent to improve them, according to a new study from Transportation California.
Last year the state's roads were third worst in the nation. With 37 percent of 168,000 miles of state and local roads rated poor, the state has fallen to dead last on the list, according to The Road Information Program, which prepared the study. Other states in the bottom five were Louisiana, 27 percent; Massachusetts, 25 percent; and New Jersey and Missouri, 21 percent.
``A generation of underinvestment in California's streets, highways, overpasses and bridges has resulted in a shameful deterioration of what once was a showcase transportation network,'' said Larry Fisher, executive director of Transportation California, the state's leading transportation advocacy and public education organization.
(No more Olmert! No more Kadima! No more Oslo! )
Five out of the ten worst metropolitan areas ranked for road conditions are in CA. This is from 2005:
"The ten urban regions with at least 500,000 people, which includes the city and its surrounding suburbs, with the greatest share of major roads and highways with pavements that are in substandard condition and provide a
rough ride are: Kansas City – 71%, San Jose – 67%, St. Louis – 66%, Los Angeles – 64%, San Francisco-Oakland – 60%, San Diego – 58%, New Orleans – 55%, Boston – 49%, Sacramento – 49% and Oklahoma City –47%."
http://www.tripnet.org/RoughRoadsReport052605.pdf