Sunlight passing through a screen will be diminished somewhat.

In areas that can be very bright and hot, such as parts of SoCal, it can actually be beneficial for even full sun listed plants to have some protection. Shade cloth is often listed in various percentages for the sun blocking amounts. 30-50% can be fine for many plants, such as sun grown vegetables, especially if there are a lot of sunny days in your area. If you are close to the coast and experience frequent and extended overcast conditions, the extra screening might be more shade than true full sun plants would prefer.

It is difficult to tell from the photo the percentage of shade your screen would provide. The color of screening matters a bit, too. Maybe you can compare it with some various percentages of shade clothes that are sold at garden centers to get an idea of the shading amount your screen provides.

There are ways to determine light levels of an area using camera metering, but that gets a bit technical to explain. You can search for sites that explain how, and are similar to the way it can be done for indoor plants: Greenery Unlimited | How to Measure Light for Plants (lazily, just the first site I came across--there may be better ones) It might give you a sufficiently close idea between screened vs unscreened.

Thanks, gyr_falcon - that is food for thought! There must be a way I can do this - I'll bug the master gardeners again.