It usually takes about 15 minutes to go through security at PSP. However, during busy times it can take up to 30 minutes. The reason it takes longer during busy times is that there are more people trying to get through the checkpoint, and the TSA agents have to screen each person individually.
The good news is that the TSA has been working hard to make the screening process faster and more efficient. So hopefully, in the near future, it won't take as long to get through security.