This place is great in the warmer months--it has an incredible garden in the back and breezy summery drinks (e.g., sweet tea and all sorts of tequila). The menu is great, even from a California/Southwest Mexican food snob perspective. And the bar is cozy in the winter. The staff is also friendly and plays good music. Atmosphere is quasi-1890's frontier.
Update: After their renovation of the backyard and staff changes, I have to say that Cantina has taken a dip in the quality of the food and service. Some of the waitstaff from the opening is still there and very good, but the newer waitresses they've hired are not as great as the original crew.
Somehow, the bar crowd also went from refreshingly hip to baby boomer in the last couple of months.