IMHO, if you have woodies in the area, they will find it on fly-bys if you put it out. As TODDM mentioned, just give them a good flight path with sight line.
Years ago the DNR here began placing houses on the back sides of road signs along the freeways. I read then that they were very successful and they attribute part of the wood duck recovery to that initiative.
Also, experience with wood duck houses placed in my ponds on steel posts, without predator guards, have never had an issue. But I don't know what you folks down south have for snakes vs what we have up here. Suppose that could make a difference.
