The Middle Deschutes is hit and miss. Around Steelhead Falls is a safe bet and worth going early morning and evenings. Morning is mostly a nymph game with a Frenchie, Soft Hackle PT, Jig Napoleon, Micro May and a bunch of Perdigons, varying the color and beads to meet your needs for the moment. 
What are those “needs” you ask. Depth. Water Speed. Light Intensity. Light Penetration in to the Water. These can be/will be/should be factors on choosing the right Perdigon or Jig to fish. 
Evenings will be similar here as on the Lower D. PED is often my favorite hatch in the summer on the middle. 
PMD, BWO, Caddis are all likely to run in to as you head out to the river. Rusty Spinners at Dusk just like the Metolius. 
Renegades, Stimmy’s, Purple Haze and a Float & Fool are good flies to use as attractors for Middle D fish. A Light Cahill is a wonderful fly for here as it rides riffles well and imitates PMD’s and Pale Evening Duns in choppier riffles. Watch water temps for safe handling of fish on the Middle D. Some areas are going to be too warm until you get the rejuvenation of the springs upstream of Steelhead Falls. Fast Water through the Riley Ranch near Bend is likely going to be just fine too. 
As a reminder, if the water is over 68, it is not safe to C&R trout. if you do not have a thermometer you need one to fish trout waters in the summer.