The Deschutes above Benham Falls will open on the 22nd, and that section is really more like 3 seperate sections in terms of how to fish it. From Wickiup Dam down to Benham, it will mostly be a subsurface game but you will start seeing mayflies there soon as it warms up. PMDs and a similarly sized but dull pinkish mayfly will be the most common bugs, but you get goldens and green drakes as well going into June. Terrestrials are also kind of an under-utilized fly out in this stretch, so if you see any ants flying around or crawling on logs near the river, don't be afraid to toss one out there. Above Wickiup, it's a lot of streamer fishing and covering water since most bigger fish will be hanging out down in the actual reservoir rather than the short section between Crane and Wickiup. Behind the Crane Prairie dam can be worth a shot if you feel like fishing this section. Above Crane Prairie, you'll see terrestrials and golden stones, but euro nymphing or fishing small streamers is typically the most effective way to fish this section. Stealth is of the utmost importance if you want to catch the bigger fish, and yes they can sense your footsteps from pretty far away so go slow and take your time when approaching any water that might hold fish.
Fall River below the falls
There typically aren't a whole lot of fish down in this section, since the Cape Cod stock of hatchery trout put into the Fall are chosen for stocking because they don't stray far from where they are stocked. If you do choose to fish down there, all the other bugs you see above the falls are just as effective down below. PMDs, some green drakes, terrestrials (especially ants) and san juans are always on the menu in the summer months. Streamer fishing can also be an exciting way to fish around the deadfall and cutbanks. Stealth is very important here, and you might only see one or two fish in a day so be cautious when approaching likely holding water.
Metolius above Allingham
All of the same bugs you'll see in the upper section from the Gorge Campground up to Allingham. Mostly PMDs and caddis, but certainly golden stone nymphs, terrestrials, midges, and eggs can work day in and day out up there. A few green drakes but not as many as you'll find below Canyon Creek.
Tumalo and Whychus Creeks
Nothing much to worry about here other than runoff, which could certainly still be a problem on the opener. Other than that, fishing attractor dries and nymphs is fine enough for these less selective fish.