I just got back from a drive through DeSoto to confirm the section of road that is off-limits to non-motorized vehicles. Going west on 83rd street, the off-limits section begins at the top of Cedar Creek hill just east of the red house with the built-in lookout tower and extends west 2.5 miles to just east of the intersection of Kill Creek road near the Engineered Air manufacturing facility.
I only know of three ways to get around that section.
1. Go through Olathe and take Kill Creek north to get back to 83rd street.
2. Go through Bonner Springs taking Loring Road south to an intersection where Loring road turns right. Continue on Loring westbound to County Road 2. Turn left on County Road 2 and follow it south about 2-3 miles until you reach Wyandotte road. Wyandotte takes you south to the river bridge that crosses over into Desoto. You'll reach 83rd street in a couple of blocks.
3. About .5 miles before you reach the prohibited section of 83rd take Cedar Niles south. Then take a right at the second residential street and follow it west to Cedar Creek road. Turn left but beware, you'll have to ride a mile of gravel to get to the pavement where it turns into 95th street. Follow 95th to Kill Creek where you'll take a right to get back to 83rd.
You might Google these routes to clear up any confusion I've caused. I hope this helps.
DD