SD’s demographic data & average income are very close to the ones of CA. If you are planning to conduct some researches in the West Coast, SD will be one of the best places for you.
California Demographics (2011)
Median Household Income (2017)
Note, The median household income in LA county is lower than SD because of the significant income disparity in LA county. The living cost in the urban area in LA county is typically higher than SD.
Data from the U.S. Census Bureau American Community Survey 1-year estimates for 2017