The Wayback Machine - https://web.archive.org/web/20140503024932/http://library.csun.edu/Guides/GovPubs-SFValley

San Fernando Valley Statistics and Facts: Overview

Understanding Valley Geography

The San Fernando Valley is a geographic area (see map) which includes several cities and a large portion of the City of Los Angeles. In addition, the communities we commonly list as a "city" in an address, such as Northridge, are actually communities within the City of Los Angeles and do not meet the defintion of a "city." This political reality can make finding information about the San Fernando Valley a frustrating and/or time-consuming experience since the boundaries you may want to use for the Valley or a community within it may or may not correspond to the boundaries used by those who have compiled available statistics and facts. Always check to see what geographic boundaries were used when the data was collected. In many cases, smaller areas, such as city planning districts, zip codes or census tracts may need to be used to define the geographic area of interest and then the data for each of these smaller areas added together to get the total you want. 

Links for cities at least partially in the San Fernando Valley