"¿Que onda?" is an expression mainly used in Mexico, but also (at least) in Chile and Argentina. It has many other meanings appart from "what's up?". I'm from Spain, and here this expression is not used.
In Spain, we would say "¿Que tal? ¿Que hay?. And, in a teenager context: ¿Que pasa (tío/tía/colega)?