I really used to swear by Casa Don Juan for lunch, dinner, drinks, late night...I even had my wedding weekend happy hour dinner there....but recently the service has taken a nose dive. The waitresses are eager to push increasingly low quality guacamole on you and if you turn it down they really can't be bothered by you.
However, the food has remained really consistent. The portions have shrunken a little bit on more expensive items (Fillet Veracruz), and when produce gets expensive they certainly cut corners...but if you know these things and order accordingly, you'll have a solid meal. The pitchers of Hornitos margaritas don't hurt, either.
Really, if the service and the produce conditions increased, this restaurant would get 5 stars.