Uh, come again?
You have no legal right to drive down the street and follow people and ask them what they are doing...
Nonsense. What law is broken when a person walks up to a stranger and asks "Excuse me, do you live around here?"
...cops even need probable cause.
You are being vague and stupid. Beat cops walk down the street and look at people or say hello all the time. They need no probable cause to do this. Now if they detain you, enter your home, pull you over when you are driving, other specific situations, yes they sometimes need probable cause. But just to say hello to someone walking down a public street? Of course not!
But this guy can get out of his car and mess with you...
Again you claim that Zimmerman "messed with" the kid but you have no knowledge to back this up. There must be some reason why you insist on saying one stupid and dishonest thing after another. I'm guessing that you are probably stupid and corrupt but perhaps there is some other explanation.