The best meal I have had in six months of living in Berlin was hands down at Neugrün's Köche in Prenzlauer Berg. They do a four course menu that is either a local Berlin/Brandenburg menu or a southern German inspired menu. It's expensive but completely worth it. Another great place (not in Prenzlauer Berg but with the public transportation here who cares) is La Crapule in Kreuzberg. They do a 9 Euro lunch with three courses. I'd also like to second the vote for Morsi e Sorsi, it is my favorite wine bar in a city with a million of them. For another non-P'Berg recommendation, since I think you have enough of those, hop on the U2 to Schöneberg and go to the Green Door. They have the best cocktails in Berlin and it's a lot of fun. Just ring the bell by the door. Berlin is a great food city, but as a fellow California native I have to say that there are better types of food to focus on while you are here than Mexican. Maria Bonita seems to be the one exception, but I haven't worked up the courage to try it yet since I have been so disappointed by the others.