Brake light switck?
 

Will the brake lights still work if the switch is bad?
My problem is the cruise does not turn on!

It's likely that the brake lights won't illuminate with a faulty switch. When you say "bad" do you mean it never works, or it won't shut off? Do you suspect the switch is causing your cruise control issues because pushing the brakes is supposed to deactivate cruise?

Yes!
I replace the brake light switch!
Brake lights work, except center high mount is not working?
The reason for replacing the BL switch was to get the cruise control to work, which it still does not.
Could it be the C H M not working, be the culprit?
Or is it the switch itself the cruise light does not come on ?
Help????????????????????????????????

I doubt that the CHM not working is interfering with the cruise control. Although you may want to use a tester to see if current is actually reaching the third brake light to determine if the light itself is faulty, or if the signal isn't even in the wires.
If your cruise light itself isn't coming on, perhaps it also is burned out; my cruise control does work but there is no dashboard light to say it's on or off. So perhaps it is the switch itself in the signal stalk. What year is your Montana? I have the 2003 factory shop repair manuals and could look up any troubleshooting tips.