I see you've gotten all the appropriate must-sees for San Diego!
I live here. I also freaking HATE Horton Plaza. Its local nomenclature is The Escher Mall.
If you like Mexican food, you are going to love me for sending you to Pokez. It's cheap and incredible--and no one knows about it. Take Broadway from Horton Plaza, and turn right on 10th. You will see it on the right. Go there with a bunch of friends and enjoy. (I recommend the Chile Relleno.)
Oh, and if you have friends of the persuasion, it has a very vegetarian-friendly menu!