Yeah sometimes we get santa ana winds but that's in late fall. Do you think its enough ventilation as is?
I used to live in SoCal, so allow me to recommend a different route for you if I may.
Building your own greenhouse is not only cheaper, but a way to tailor it to your own needs. If you use plastic sheeting greenhouses without fans, you'll create a hotbox that will kill them in short order. In SoCal, without proper ventilation in the form of fans then that greenhouse can get to 120-130 degrees in 90-95 degree ambient temps.
Instead, build a frame out of 2x4s. Then, grab yourself some 50% shade cloth on Amazon and staple it to the frame. Not only will this be cheaper, but the shade cloth will serve two purposes for your environment. 1) It will help with the intensity of summer and 2) airflow throughout the entire frame instead of a handful of exhaust holes.
If you use plastic sheeting for a greenhouse without a proper source of ventilation then you will be at the mercy of the greenhouse effect. I use plastic sheeting in my greenhouse, but I not only have proper ventilation but an evaporative cooling wall as a passive intake. The only reason I'm not using a shade cloth greenhouse is because of my need to control the smell. Otherwise that's exactly what I'd be doing, because combined with a misting set up it is the cheapest and simplest way to grow outdoors.
This is also strain dependent too. Unless you have a need for the privacy a greenhouse offers, the best results to be had in SoCal outdoors would be to find an Afghani or Sativa that will thrive in that weather and forego the greenhouse entirely.
