We have done the I-15 to I-84 to 20 across to Bend several times. This is a good route but you'll have to go through SLC which is almost as bad as going through Los Angeles.
Another route you might want to think of, is taking I-40 over to Barstow, Rt 58 to Hwy 395. North on 395 to hwy 20 and over to Bend. Only major city on this route is Reno and it's not bad getting through it.
FWIW, Hwy 99 is bad, heavy traffic, construction, etc..... I-5 also has some very bad areas....not to mention very boring.
We use Hwy 395 to go to Oregon almost exclusively. The eastern Sierra's are magnificent!
Ron
Ron & Sandie
2013 Tiffin Phaeton 42LH Cummins ISL 400hp
Toad: 2011 GMC Terrain SLT2
Tow Bar: Sterling AT
Toad Brakes: Unified by U.S. Gear
TPMS: Pressure Pro
Member of: GS, FMCA, Allegro
RETIRED!! How sweet it is....