Lots of good advise above. As was already stated May-June are runoff time and the rivers are often high and muddy,especially the bitterrot. However if you catch the runoff on the receeding side ,particularly on Rock Creek you have a good chance of running into the Salmonfly hatch which can make for phenomenal fishing. As others have stated I encourage you to at least bring fly rods. The Salmonfly hatch is a great time to fall in love with fly fishing. With large trout comming up and splatting anything big and orange on top.
Spinners will ofcourse work very effectively for you but take a good supply of them because te fish will be on the banks and I don't mean a foot out more like 1 or 2 inches or even under the bank! You will lose lots of spinners. Unless your a pro bass fisherman and can put a lure anywhere you want from a moving boat. However you decide to fish please use only single barbless hooks and no bait!
shuttles are easy to arange for about any stream you'd want to float.