Since I live in Olde New Mexico, SF's Mission District (which is closer TJ North, apparently) I am supposed to be swamped with fantastic Mexican cuisine, yet I must say that the Central American restaurants pretty much blow the tourist-swarmed Mexi joints out of the water these days. You know you are in for something slightly more "authentic" when you step into the restaurant and a bunch of off-duty painters in their work gear watch you come in, watch you sit down, watch you look at a menu and watch you start vacantly staring around for a waitress. Then they get back to their gabbing. Then the waitress speaks no English, forcing you to deploy your pathetic taqueria-Spanglish.
Los Palmas on Mission St. by 23rd, TRY IT! (It's actually not the stare-at-you place, that's down on 19th)
Cash only.