I'm thinking 'Live and let die' was one of those themes.
For mariachi dragon (yeah, I'm from Arizona so I actually know something about Mexican and Hispanic culture) you could go with a dia de los muertos motif or something in a myan or Aztec: or go with a Pancho Villa look ("It is better to die on your feet than live on your knees."). Or more of a cartel sort of look. Like the yakuza they also have ink down to their balls: so if it's a Japanese character, you can play with the similarities. Mexican Catholicism is a mixed bag of myan traditions and catholic mythology. You could harness that kind of imagery. Also you could have her be from the Philippines, a.k.a. the only place in Asia where Spanish is a second language. Or she could be from Hawaii where gauchos were employed during America's Imperial hey day.
For the noir character, I'd research California in the roaring twenties. Maybe some Charlie Chan or Fu-Manchu. If you're going for a pulp character that is. 'Chinatown' with Jack Nicholson is also a kick ass avenue to explore for a character like this. If that's what you're going for.