Where in CA are you leaving from? It may not be as convenient to stop in SLC unless there is a specific reason. If you are going from SF bay area, then Hwy 50 (aka loneliest hwy in America) through Nevada will link right into I-70 near the start. Hwy 50 is a nice drive up through Tahoe area. If you take I-80 it is just as boring, but is 4-lane interstate vs hwy. Hwy 50 is actually kind of nice to appreciate the desert, but it is pretty desolate with a few small towns.
I have driven from SLC east to CO and taken the hwy 40 route. Very beautiful, but it does go through some small towns and takes a little longer time. You can drop down to Dillon on hwy 9.
I have also taken the route south from SLC to I-70. You go SE on hwy 6 out of Provo (actually a tad south of Provo in Spanish Fork). Hwy 6 is beautiful drive through the mountains from there to Price, UT area. The it is pretty boring flat desert until you intersect I-70 at Green River, UT. Moab, UT is just a little south of I-70 east from Green River south on hwy 191. I-70 is a pretty drive and drops you right into Dillon.
I drive the hwy 6 route every year on my way to Bonneville Salt Flats, it is a good drive. I guess the route you take is just depends on what you want to see more of, and if you like hwy or interstate.
