Bunzo, didn't mean to ignore, sorry. I can't tell you anything about the Boise area, but what my son explained above regarding the Henry's Fork should be helpful. Several fly shops you should visit while in eastern Idaho would be Jimmy's All Season Angler in Idaho Falls, Rene' Harrop's Trouthunter in Island Park (Last Chance, right along the river), and Mike Lawson's Henry's Fork Anglers also in Last Chance right across the street from Harrop's place. Any more specific questions, PM myself or my son, mgliss, and we'll be happy to give you what info we can about the Henry's Fork, both upper and lower rivers.
Kelly.
Tight Lines,
Kelly.
"There will be days when the fishing is better than one's most optimistic forecast, others when it is far worse. Either is a gain over just staying home."
Roderick Haig-Brown, "Fisherman's Spring"