Fred--I assume you mean signs for roads crossing streams, as opposed to trails. There wouldn't be all that many road signs, since there aren't that many roads in/through the Park. On the other hand, trail crossings exist in great number. I seem to have vauge memories of a few trail crossing signs when I was a kid, and I know some of the creeks had signs at trail heads saying things such as "15 fords". Many of the fords also had names. On Deep Creek, for example, 1st Ford, 2nd Ford, Deep Ford, Perry Gap Bend Ford. Of course all of those are gone, thanks to trail changes.
I personally don't know that such information would mean much to road travelers, although you never know. On Friday a van full of Japanese pulled up to me above the "Million Dollar Bridge" on Straight Fork and insisted they could go on up the one-way road from Heintooga Overlook the wrong way to get to Mingo Falls. I finally dissuaded them--language was a big problem--and told them they had passed the turnoff for Mingo Falls a good many miles back down on the Big Cove Road. Obviously they could have used some signs, although there are small signs indicating the turn for Mingo Falls and a big one saying Mingo Falls Campground. This isn't the Park but is on the reservation, but it's indicative of the problem. When the guy didn't understand "hard surface" or "pavement," I knew he was in trouble. I wonder if they ever found the falls, although I did get them convinced not to go to Heintooga the wrong way.