If you're in SoCal I'm guessing we have comparable weather patterns (I'm in Perth, Western Australia - so feel free to check). With what I'm about to type you need to keep in mind that north and south references are different for each of us...
- Recommendation is for hives to get early morning sun; My hive gets midday to late afternoon sun, no early morning sun. In winter my hive only gets indirect sunlight, no direct sun
- Recommendation is for hives to be exposed to the north (to get maximum winter sun); my hive has no northern exposure and sits on the south side of my house
- One of the bee keeping courses I've done down in Margaret River (google for weather; likely cooler than you; it's cooler than me) had the hives located under a peppermint tree with only dappled light. The area the hive was located was that cool the ground appeared to be semi-damp. I think it was located here more for protection from the wind. The consequence of shade vs sun was a secondary consideration
Now, given that I am a bit anal (do you use that expression?) before I got my hive I actually bought cheap temp and humidity data loggers from eBay and monitored 4 potential hive locations on my property over a 10mth period (only the peak of summer was missed, which I didn't care about). Where I located my hive appeared to have good temperature stability year round and was largely shielded from the wind. Sun exposure was a secondary consideration for me (in summer we can still get 30+ degC in the shade here...).
...and in my first year I got over 40L of honey and about 8kg of honeycomb.
So, assuming the area you locate your hive in has reasonably stable temperatures, doesn't get too damp/cold, isn't exposed to the wind (Freo Doctor here) I wouldn't be too concerned about the shade. This being said, if you notice your colony strength weakens you might need to reconsider your selected location. I'm guessing the biggest impact of a shady location with slightly cooler temps will be the bees using slightly more of the honey stores to keep active and maintain hive/colony temperature.
Did you have a photo of the area you are planning to place your hive? That might elicit a few other opinions...