Chris.....a couple of thoughts...given that you expect to be in Utah, I would suggest you add a ride around the Slickrock Trail in Moab. Its a classic mountain biking route (12 miles) but was originally used by motorcyclists and the DRZ would be perfect. It will be hot in July which will keep many cyclists away. Also lots of other routes and trails in the Moab area (Porcupine Rim, White Rim). Completely different from anything in Blighty.

Also, in Idaho, consider the Magruder Corridor trail. Crosses the largest wilderness area in the states. Is west of the CD Trail but would give you a side option that you could link into the Lolo Pass route. (e.g. CD Trail to Missoula, over Lolo, across Magruder and cross country back onto the CD near Wise River) Here's a link to a map of the Magruder route MOTOWHERE?

Also, you might consider aiming for and leaving the bike in, Portland, before flying to SF. Would allow riding through the Columbia Gorge and up along northern Washington into BC near, say, Grand Forks, with Nakusp then about 1-2 hours north. Then a little highway riding into Kaslo, a stop at Ainsworth Hot Springs and across the ferry (free) to Crawford Bay and onto the Grey Creek Pass route into Kimberley would then set you up for Roosville and the start of the CD trail heading south. I took a week to ride from Roosville to southern Colorado using the CD. Here's a few pics from that trip.

Good luck with your further planning. You'd be welcome here (Red Deer) but it's probably too far off route given your schedule. Maybe see you in Nakusp.

Stephen