Flacos is a little house divided into a kitchen, a counter, and a small indoor seating area (maybe 15 people max could fit inside at once). It's cool you can see exactly what's going on with the food but can definitely get cramped. They also have several tables outdoors if the weather is nice, and are in a parking lot so parking is easy, and very near a BART station if you prefer public transit.
It's quite casual, order at the counter and bus your own dishes. The food and people there seem very authentic to Mexican cooking, unfortunately for my taste it is too authentic, featuring a lot of fried food and fillers. It's definitely not fresh "California style" Mexican food, and didn't strike me as healthy or satisfying. Although I wouldn't go back, I can see why people who enjoy this type of food would love Flacos.
Cons: Not a great value