You are the only one that would know since we can't see it. It could be coming from many places. Such as water pump, radiator, hoses, freeze plugs even a crack in the block. You are going to have to clean it up and start looking. It's not likely to be the heater core or the coolant would be leaking in the cab on the passenger side floor.
Alright if it was leaking from the water pump where should I be looking?
If it is the water pump they will normally leak at the weep hole. That's on the bottom of the water pump at the pulley shaft neck. It is a little hard to see unless you have a small mirror and a flash light.