Is it possible i have sad (seasonal affective disorder) even though living in sunny san diego?

Yes: You r probably better off than u would b in a locale with lots of overcast days treatment is usually wellbutrin (bupropion) & light therapy.

Possible: People who life in climates with winter months are more at risk for sad. For some the onset of sad is associated with the decrease of the length of the day and natural sunlight. There are less common cases when people being affected during summer months. I would recommend talking to your health care provider who can make a correct diagnosis based on your history and symptoms.