Of course, different people will recommend different things - but unless you live up on the coast ridge like upper Topango Canyon or Mulholland Drive and use natural ventilation with the ocean breeze rather than A/C, you certainly want at least standard double-pane windows, and likely heat mirror or equivalent at least on the sunny sides. If you live out in the hot side, say out towards Simi Valley or Sylmar area or south of the 405 or at least south of the I-5 and out towards Pasadena and San Berdo, triple pane or a high-efficiency solar screen film window may well be economic or more comfortable for you.
This assumes of course that your house picks up a lot of solar heating - if a mission with courtyard or a thick-walled stucco or adobe which does not heat up a lot in the summer (which for your area about 6 months qualifies as that, at least), or if a modern house with few or very small windows on the solar exposure side (southward for most houses in your area because of the mountains on both sides, unless you are out in the middle of the valley), you may not need as energy efficient windows.
Don't forget, if desired/needed, ultraviolet protection as well, to protect furnishings and flooring and such from severe fading - again at leat on the windows on the main sun-facing sides.
I suspect - no am pretty certain just because of the nature of CA politicians, that there is probably a California energy standard mandating at least double pane and probably heat mirror too. Yup - here are a few links to get you started on that - and just because a certain energy efficiency is required don't assume what you are offered or is delivered will meet it - there are a lot of fly by night and unscrupulous contractors out there, especially with the large number of unlicensed ones in your area.
http://www.energy.ca.gov/2015publicat...
http://www.lacantinadoors.com/blog/en...
http://www.energy.ca.gov/title24/2016...
