Yep, Thunder Valley is near Denver. Actually, its about due west of it just up against the foothills before it gets real mountainous at the intersection of I-70 and C-470.
The Colorado trails are be similar to your neck of the woods: bone dry and loose.
About the KLR, I actually just sold it a couple of weeks back. Great bike for what it is: a true 50/50 dualsport. Things were changing for me to the point where it didn't make sense to keep it (less weekend time, more highway time and needed cash). It's a shame there are so few options for bikes like it. If the BRP had the button, I think I would've gotten it instead and that could've been the all-in-one bike. What was Honda thinking?