I've tried a complete rearrangement, so that the overall effect is more positive about the restaurant, reversing each couplet apart from the last:
Though the customers are sober
Where Desperados are drunk
And crimson candles light the tables.
Where a stack of logs is untouched by fire.
Though Sombreros stay nailed to the walls
Above the hatless waitresses in red and black
And though guitars remain unstrummed
Where loud piped music sounds,
Outside is cold wet November
And inside is dry warm Mexico.
I think it's better, though it needs a bit more tidying up. I've also change moist to dry. Moist just doesn't seem right. How often I'm reduced to saying, to myself or to students, 'doesn't seem (or sound) right'. Not sure how helpful that is but sometimes it's the only way to express it.