Go for the margaritas, the socialising and the food - in that order. Wooden tables and red candles give Penas a Mexican-hacienda feel. A major attraction is the flavoured tequila (coffee, mint and vanilla) poured from a huge decanter at the bar. The food is decent, but the burritos and enchiladas appeared to us to be pre-made. The nachos, however, are some of the best we've sampled in Frankfurt.
