TH77- I know the boat that you're in. I'm 18, and I've only been fly-fishing for about 5 years. Kind of tough and frustrating starting out when the fish don't bite.
Try pheasant tails and hare's ears (beaded and regular), zebra midges, and scuds. Wooly buggers or mohair's in black and olive are a must. White or tan also. Remember to keep the nymphs close to the bottom.
Dries don't produce nearly as many fish, but are fun to use. Elk hair caddis, adams, and stimulators might be considered, but aren't necessary to catch fish.
If you are just starting out, I would suggest staying in the park. Yes, there are some bigger fish outside, but the river is harder to fish. I have had 100+ fish days in the park before, and I got skunked outside the park over the summer. Just hone your skills in the park for a while, and maybe move outside if it gets too easy.
Rob