Don't go by yourself to RP
Alan, if you've not been there before, I wouldn't suggest going to Road Prong by yourself. Its choked with Rhododendron and if you don't pick the right spots to get out of the stream, you may be fishing for hours until you get to a spot you can finally exit.
If you have a limited amount of time (less than 4 hrs) I would suggest fishing the WP of the Little Pigeon below the Chimneys Picnic Area (about 2 miles closer to G'Burg). You could pull off near the road to the picnic area, hike down the road a bit, drop down to the stream and fish back up to your car. Through that section you should find lots of rainbows and a few brookies as well.
Bring lots of #16 Yellow Stimulators or PAs (or your favorite fly of choice).
Save the trip to RP for another day when you have lots of time.
"Even a fish wouldn't get into trouble if he kept his mouth shut."