There are 33 California congressional districts that had one Republican and one Democrat running in both 2012 and 2014. If you take the current Republican share and average it, Republicans have improved by 4.1%. So they cut the margin by 8.2%. If the shift were uniform, Republicans would win CA-7, 26, 36, and 52 and be even in CA-3. It's not uniform. Republican improvement is below that in all these districts, as well as CA-24, 41, and 47. It matches that in CA-9 and exceeds it in CA-16.
The districts Republicans showed big improvement in wee a mix of safe Republican and safe Democratic districts. I made light of Democratic GOTV efforts, but it's possible that they did have superior GOTV despite it being harder to get their people to the polls. So while Republicans were improving in Grace Napolitano's CA-38 by 8.9% and Ed Royce's CA-39 by 11.0%, Democrats kept that down in the competitive districts.
The tide clearly reached California, but the Republican party might not have taken advantage of it.
Edit: It clearly helped Democrats that they outspent Republicans by anywhere from 3 to 1 to 20 to 1 in some of these districts. Imagine how well Republicans might've done if they had enough money to do advertising or even hire a staff.