Just to clear something up, the rivers are open the last saturday of May not the 15th of July. Thats the general opener but there are some rivers/tribs that do open later but for the most part May is the opener. If you are in the West part, Blue Ribbon is your best bet. They are good people and great guides. Around gardiner there arent as many guides but really, Yellowstone is the best place for DIY fishing and June is the best month cause its before the tourist hatch. Goog luck and if you need any more ideas you can pm me, i spent a lot of time inside the park over the last six years