A few more things I've thought of (more than likely, some forum members make a living with SEO, so additional info is welcome).
Your only keywords are (on the AR page too, so why use English "best"?): argentina, best sushi, buenos aires, greengo, mejor sushi, sushi
You can add sushi palermo, sushi barrio norte, sushi gourmet, sushi belgrano, etc.
You can put keywords too in alt tags of pics (just a few), if there are.
And pay some guy looking Japanese to take a knife & sushis in front of a logo of your business and take a pic?