What's the difference between "qué onda", "qué tal" and "qué pasa"? Don't they all means "what's up" in Spanish?
Lots of ways of saying "what's up" and other slang greetings in Spanish:
¿Qué tal? - What's up?
¿Qué onda? - What vibe?
¿Qué pasa? - What's happening?
¿Qué hay? - What is there?
¿Qué hay de nueve? - What's new?