I am not from Dublin but I do frequent. St James hospital is southside on the road from christ church to the red cow roundabout. Traffic is usually minimal around this spot. As far as i know it quite close to Guiness house and Kilmainhaml. Once you pass the red cow you continue for about a half a mile until you reach a righthand turn in an area with shops and pubs and things, turn right here and you'll hit it after a half a mile. Ok drunken directions but 90% correct. hehe best of luck.