Your local Extension Service office will have lots of info about homegrown citrus.

You can locate contact info by using the interactive map at http://npic.orst.edu/pest/countyext.htm 

For San Diego County, the free Master Gardener hotline is at
(858) 822-6910.

Lots of cultural info, as well as help for pest problems , here - http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/citrus.html

Hey a happy camper! Nice to see another forum member from San Diego.

For my navel orange (and other fruit trees)I am using soaker hose in a spiral pattern around the edge of the canopy and about halfway between the canopy and the trunk. I am in East County and it can get warm in the summer. Right now I have to check under the mulch to make sure things are drying out but other times of the year I don’t really have an issue.

From what I have always read you do want to get both sides of the tree watered. The master gardeners asssociation has some pretty good info on their site. (Posted above by jean)

What sort of soil do you have, and how much rainfall does your area get?

When trees are young in the ground, water near the trunk and out to the drip line. ROotball is exposed to the elements when trees are younger. When trees are more established and have developed a canopy you don't need to water as much near the trunk. Water out to be drip line and a few inches from the trunk. MOre established trees need deeper watering especially in the summertime.