The picture seems to be of the area below the alternator mount bracket. I am not aware of anywhere that coolant can leak below the alternator bracket. I would chance to say that you may have a leak from the thermostat, water pump, or coolant hose from up above the alternator, and it is drizzling down the block and behind the alternator bracket, then to the ground from there. Id be looking somewhere above the alternator for a leak.