The last time I went from SD to LAX on a weekday (non-friday), it took a bit over 2 hours. (Road) travel wasn't extremely heavy. On a Friday, I'd probably leave San Diego at 11am (just to be safe) and not have to rush. If you have to check in luggage or return a rental car, that should give you enough time.

LAX airport is convenient from my experience, but you can't predict it. One time, the security line was really long and I went straight to the elite status line (much shorter, but it was still a line). By the time I got through, most people have boarded (I was the last of the two to board). I was only off by a few minutes, but it's it's actually one of few times when they either boarded earlier/on time rather than late. Go figure.