El Zocalo has great food, but it's the patio and margaritas that are the real draw. On a spring evening it's absolutely wonderful to sit out there among the bouganvillas and jasmine, listening to the fountain and maybe the soft music of a mariachi band. They have a wide variety of specialty margaritas: my favorite is the raspberry margarita made with Chambord.
The food is very reasonably priced and the portions are large enough to share. My friends and I like to go there and share 2 or 3 appetizers, which are more than enough for a meal.
There tend to be waits on the weekends, but if you go on a weeknight there is usually not a crowd at all.