I would highly recommend you go to the Owyee River, which is just over the border in Oregon. I and a group of friends take a ten day fly fishing trip every year. We have fished all over Montana and Idaho. We intended on fishing the Boise area last year, but the water was too low in most of the rivers. A guy recommended the Owyee River in Oregon. The Owyee was without a doubt the best fly fishing I have ever had. Huge browns and Rainbows. We fished from below the Dam on down a couple of miles. It is a small river with plenty of access. I believe it would take you about an hour and a half from Boise to get there. We fished it last September, July will be real hot in that Desert Canyon. Plan on camping unless you want to drive a distance from a motel. You can camp below the Dam, or drive up the road to just above the Dam and there is a state park with RV hookups and showers.