Welcome back to the RTA forum!
The drive from Seattle to San Diego is spectacular. However, it is also 1250 miles via I-5, meaning the fastest possible route would give you 3 straight 8 hour days behind the wheel. That doesn't include time to drive any of the Pacific Coast Highway or stop at anything else along the way.
If the idea of a speed run trip, where you get to see the west coast as you fly by it at 75, appeals to you, then I'd say you should drive.
However, if you'd rather spend your weekend relaxing and if you think you'll have another chance to spend some more time near the Pacific, I'd say you should enjoy San Diego's perpetual 75 degree and sunny weather.