Don't go to the Dragon's Den near Petco Park. For average sushi/Japanese, they have really terrible service.
My friend and I get there and we are famished after a full day of the con. Not busy, so we get a table outside. Long pause before we get our drinks ordered. Then another long pause before they take our orders for dinner and an appetizer. Appetizer comes, no prob. Then my friend got his meal first (ramen), then he starts eating and I wait. And wait. And wait. He finishes his meal after about 15 minutes and I still don't have my food. Then I wait some more. Finally, I complained to the waitress since by this point, other tables have been seated and already had their food. Apparently their sushi bar was badly understaffed. Oh and a glass fell from another table and no one came to sweep it up, just leaving broken glass on the ground for several minutes. My food finally came and despite being famished, I thought the food was pretty mediocre to average at best. So the wait was not worth it.
They did take off 25% for the long wait for food but I can't recommend this place since there are so many other places with sushi that can at least provide some better service. For what it's worth, my friend thought his ramen was good.