Apparently the word
hola, although technically proper, is not typically considered a
masculine thing to say. Upon greeting a passing
Mexican co-worker with this expression, his response was
¡No, no, 'hola' es para niñas! Los hombres se dicen '¡Que pasa!'
(Translated: "No, no, 'hello' is for little girls! Real men say 'What's up?'")
So there you have it, another item in the long list of things you never learned in Spanish class.