As of the most recent voter registration report from California Secretary of State Alex Padilla, voters declining to state a party preference make up 24 percent of the state's registered voters. That is nearly a 3-point increase from this time in 2012.
Looking at individual Assembly districts, the percentage of no party preference (independent) voters dips below 20 percent in only a handful of districts, including 12, 21, 23, 26, 31, 32, and 36 (which include Kern, Merced, San Joaquin, San Jose, and Fresno). Five districts even exceed 30 percent, including 17, 19, 25, 49, and 80 (parts of Los Angeles, San Diego, and San Francisco).
Check out the map of Assembly districts here.
Here's the full breakdown: