If you take Frank's advice about fishing the San Juan, make sure to first check water flow levels, which can be quite high in the spring due to releases from Navajo Dam. You can get some idea of what's anticipated on the sister Forum to this one, San Juan River Forum
. Also, on this and the San Juan River Forum
, Steve Rollins of Aztec Anglers
specializes in guiding the San Juan, which would be a necessity in high water spring conditions in a drift boat, since wading is difficult and can be dangerous then. The San Juan, while scenically different from Montana in that it is a high desert plateau, is quite beautiful in itself, although you won't have snow-covered mountain vistas there as you might in Montana.
Here's another suggestion for dry fly fishing in a beautiful area that time of year: I have fly-fished in the Jackson Hole area in just the time frame you're considering (late May-early June), and found the dry fly fishing fabulous then, much to my surprise. I was wade fishing streams as they flowed into Jenny Lake. You will never find a more beautiful spot (attached cellphone picture doesn't do it justice). And there is a lot of publicly accessible water there, since much of it is in the Grand Teton National Park, Bridger-Teton National Forest and, of course, Yellowstone National Park (which has its warm-spring-fed Firehole River, which for that reason fishes much earlier than other rivers in the area). While I have not drift-floated the Snake River which interconnects these various lakes, I know Will Dornan's Snake River Angler
in Moose (website: Will Dornan`s Snake River Angler
) provides guided drift boating (exclusively, I believe) on the Snake River from Jackson Lake downstream for almost 100 miles. I can vouch for their reliable fly suggestions. Another good online resource for fishing conditions and places, etc., in the Jackson Hole area is High Country Flies
located in Jackson [website: http://www.highcountryflies.com/]
Hope this helps . . .