If you're after greenbacks and only have half a day, then the Roaring River on the North side of the Park is your best bet. You enter the park through the Fall River entrance, continue on past Sheep Lakes and follow the signs to the Lawn Lake Trailhead. There's a pretty steep climb at the start of the trip that can take a lot out of you if you're not used to the altitude, but once you hit the top it gets a lot easier and their are plenty of fish. You can call Grant at Estes Angler to get the latest info. Almost any destination that has greenbacks will require some strenuous hiking.
If the Roaring River climb is more than you want to do, then you can work the plunge pools coming down from the top. It will require some rock hopping and scrambling, but there are some nice fish to be had; just watch your step.
Dan S
"I still don't know why I fish or why other men fish, except that we like it and it makes us think and feel." Roderick Haig-Brown, A River Never Sleeps