base on this photo :

 

check the thermostat - I had a similar location (back behind firewall) and was told there were some o-rings on the thermostat. Opted to replace all together. I had some bigger issues after, but this was source of coolant leak..... check thermostat housing leaks on here. I'll see if I can locate the one I read.... Good luck

 

Thermostat housing, or weep hole from the water pump. Possibly both.

 

did you pop open the hood and look? Maybe you can spot where the drips are coming from....
Not trying to be a smart azz...but nothing beats a close look to save one from going on a snipe hunt....

 

One thing I've used to find those elusive damn leaks is to buy some ultraviolet coolant dye and put it into the coolant, then on a dark night and with an ultraviolet flashlight the leak is easy to find. (Of course, it was kin the most inaccessible spot possible.) Many coolants already have the dye in it, so the UV flashlight may work anyway.