San Diego: http://www.safeaccessnow.net/countyguidelines.htm#420

"City of San Diego

Still in development: Current version 9/17/03: Adult marijuana patients with the approval of a San Diego County doctor may keep up to 1 pound of marijuana and grow up to 24 plants. Under the measure, caregivers can keep up to 2 pounds of marijuana and grow up to 48 plants for as many as four patients.The ordinance must come back for a final vote, as a procedural matter, to be enacted."


San Diego COUNTY has adopted the State guideline of 6 flowering and 12 immature.

According to this, you can grow twice that in the city limits! I wouldn't want to test that threshold though.