Well yes, but between the call to 9/11 and Martin getting shot, we don't know what happened. Do nvs like Zimmerman have the right to ask unknown people walking through their (Zimmerman's) neighborhood what they're doing? If they are, then Zimmerman isn't guilty of anything up until the confrontation. That's just it, so far, we (and you) don't know what happened that caused Martin to get himself shot. I sincerely doubt Zimmerman simply walked up to Martin and gunned him down. Let's wait and see what transpires.
Sounds more like he was trying to avoid him. When the dispatcher asked for his address, he nervously said he didn't want to give it out because he didn't know where the kid was. That would also explain why he didn't want to commit to meeting the police in a particular place. He doesn't sound like someone eager for a confrontation.
I think ANYONE is allowed to ask ANYONE "Wazzup?" at ANYTIME