Thinking of moving, need advice. (Buenos Aires)

Hi
I am thinking of moving to Buenos Aires and would appreciate some advice.
I love to be active and would be interested in running/cycling/triathlon clubs - are there any? What are the gyms like? Are there any races/events?
How expensive is buying a second hand car?
What is there to do at weekends? Can you get out of the city easily?
Is there a big ex-pat community?
I am an international school teacher so any advice/information about the international schools would also be useful. Thanks