When it comes to building and/or remodeling in CA. everything you ever heard about from any other part of the country goes out the window.
For the most part CA. has adopted the ICC's (International Code Council) IRC (International Residential Code) but, with a lot of other exceptions, addendums, and codes specific to CA., like CALGreen.
http://www.hcd.ca.gov/codes/shl/2010_CA_Green_Bldg.pdf
More specifically Chapter 4: Residential Mandatory Measures.
As far as San Diego itself, here's the minimum code requirements-
http://www.co.san-diego.ca.us/dplu/docs/DPLU081.pdf (broken link)
This will let you know what is required of the general contractor. It's good reading for everybody across the country because, California is the originator of a lot of code that is now standard across the country. Whatever they come up with will eventually find it's way into your state, county, or local municipality.
With that being said, a few things that were previously mentioned are not allowed in the state of CA; or anywhere else for that matter. But, that's not to say people don't do it after they move into their home.
On to the question at-hand- "I wish I'd done... (this list is based on the most requested additions I've been asked to add to the construction of new homes, they are in no particular order)
*300amp service
*50gal W/H (I had requests for two 40gal- teenagers in the house) If you decide to go tankless, dedicate one for the kitchen, and depending on the layout of the house one or more for the bathes.
*Radiant Barrier roof decking
*More exterior receptacles (other than the code minimum)
*Floor receptacle(s) (at specific locations- usually in the greatroom where a console table or end table would be located)
*Home network cabling/ Cat-5 and RG-6 (even in the kitchen)
*Automation- mostly remote control lighting when coming home
*Wire and brace For ceiling fans in all bedrooms
*Recessed lighting (especially in the kitchen) Also quite popular for exterior house lighting (instead of up-lighting, the recessed cans are mounted in the soffit and wash the wall down).
*Landscape lighting (or at least the circuit to the exterior for future installation)
*Dedicated circuits for ALL appliances (like that extra fridge, or ice maker, beverage cooler, wine chiller, etc.
*Electronic or media filter cleaner on HVAC System
*Whole house Humidifier
*High efficiency HVAC System
*Security System (always had requests for additional keypads for other entry doors other than the standard garage entry door and master bdrm)
*Hoist for Foyer Chandelier (if two story)
*Intercom system
*Central Vac
* Speaker pre-wire for surround system
*Insulated garage doors with nylon rollers and rubber isolation mounts for the opener(s)
*Stained concrete floor in garage
*Master Bdrm fireplace
*Radiant floor heat- Master bath
*Lots of Hardwood flooring/ceramic tile
*Built-in cabinetry- Butler's pantry, flanking fireplaces, breakfast bars, libraries, hallway bookcases, etc.
*Partial screened-in porch/deck
*Recycling center
*Walk-in pantry with adjustable solid wood shelving- NO WIRE MESH! (Boy, did I hear that a lot)
*Custom closet built-ins
*More crown molding
*Interior french doors (instead of regular panel doors)
*solid core doors
*Lever hardware for doors
*Wrought iron balusters/handrail
*Wainscoting for mudrooms, dining rooms, garages, and kitchens
*Coffered ceiling(s)
*Trey ceiling(s)
*Brick paver patio instead of the standard poured concrete
*Interior wall sound insulation- Master Bdrm, Laundry room, bathrooms
*Landry rooms large enough for ironing
*Wash tub/sink in laundry room and wall cabinetry
* Laundry curbed and drained for washer (not just a floor drain or the washer pan)
*Driveway with extra parking area- or circle drive
*Pool and/or hot tub (or at least a circuit for a future hot tub)
*Gazebo/poolhouse/Guesthouse
*Detached garage/workshop with living space above (man-cave, apartment, office, studio, etc)
*Outdoor Kitchen
*Wine cellar
*Sauna
*Irrigation system for landscaping
*Cistern hooked to downspouts (used for irrigation)