To be honest, the beaches of SD aren't popping off right now. No storms, lower than seasonal people and no erosion. As said above you'll be better at a soccer field or community parks. If your visiting SD then by all means, hit the beach but it'll be more for the beach feel than the beach find. I live in SD and hit the beach EVERY week on sun mon and tues. 8 hrs ea day. I havent found a gold ring in over 2 months. Found a silver on the dry walk path at Coronado and found a gold hoop earring at Encinitas. That's it!
I use an excalibur 1000 and go from top of dry to about waist deep in the water. Simply put, it's close to sterile right now.
Last week I went to a park and with in 1 hr I got about 4.00 in coins (big deal right) and I found a sterling ring near a tree. If you want instant satisfaction hit a park. If you want to get burnt, get tennis elbow, and limp back to your car after 8 hrs of disappointment, go to the beach. That's the truth right now.
With the AT Pro you'll do better on the dry sand. The finds at the beach are about a foot deep right now minimum. On the upside, the weathers great the water isn't hot or cold but just right and the women...... oh the women......