Idaho 21/75. Start in Boise and go north on Idaho 21 through Stanley, a small mountain town. Get on Idaho 75 and go south through Sawtooth National Recreation area, through Ketchum and Sun Valley. You can continue South to Twin Falls and back to Boise in I-84 or you can cut east on Idaho 20 for a ride through rolling hills and high desert to I-84 and back to Boise on the interstate. Or If you want a really long ride, go north instead of south on 75 at Stanley and go up through Salmon to Missoula Montana.
The only cautions are that 21 near Boise is down in a canyon and it is fairly heavily traveled between Boise and Idaho City, a small old mining town. Take care because cares have been known to take the turns wide. The other is that this is Idaho not California so there is a dearth of guard rails on the mountain roads.
Either of these rides will give you spectacular mountain views, much of the roads are not too heavily traveled and there are small towns along the way for gas and grub. There is a large elevation gain as you get into the Sawtooth mountains. Watch for the "county Mounties" more so than the State patrol because there are more of them on the smaller state roads. The people in Idaho are friendly, we have a lot of riders so come to Idaho for some beautiful riding.
Highway 229 in California. This is a short 8 mile road between highway 41 and 58. It's a super smooth road that winds through rolling hills and oak trees.
Highway 58 is the better known motorcycle road, but 229 is my personal favorite. Every time I ride it, I feel like a kid getting off a roller coaster at an amusement park. I just want to immediately jump back in line and ride it again.
You should stay in California, that's where all the best roads are, weather too. Up here it's just 50 and raing cats and dogs right now, not fit for man nor beast.
I did get to see if my new Aerostitch Darian pants (in Hi-Vz Yaller, thank you) were water proof..(they are) and comfy... (that too) but overall it's just nasty out and really, it's like this almost all year. Don't know why we put up with it really....must be nuts.
On the plus side I'm probably faster in the wet than most of you pikers on dry roads...but I digress, no nice roads here...I hear Utah's really nice, you might try them. Just stay out of their mountains and meadows on your duel sport. They're funny about that I guess..
Everybody else, pay no attention to this troublemaker. Idaho is nothing but a bleak desert, parched in the summer and desolate as Anarctica in the winter. If the crater pocked wagon roads they call highways don't get you, crazed Neo-Nazis will. Remember every negative thing you have heard about Idaho and multiply it 100 times and you will begin to get the picture. Tell your friends to stay away, too, for their sake.