http://www.hud.gov/offices/fheo/FHLaws/yourrights.cfm
http://www.dca.ca.gov/publications/landlordbook/before-rent.shtml
http://www.dca.ca.gov/publications/landlordbook/living-in.shtml#rentincreases
In the state of California, your landlord is required to give to "timely" notice of raising the rent. If the increase is 10% or less than what you are currently paying, your landlord is required to provide at least 30 days notice, and if the increase is more than 10%, a 60 day notice is required.
With the rise of foreclosures, renting property is at an all time high, and common consumers are becoming victims. Be smart and know your rights... and trust me, in California you have SO many.
Check out the above links to answer any other questions you may have. If you have questions that aren't listed on the site, call your local Housing Authority office and they can absolutely help you.