no brakes is a bad idea as are leashes. There are a few places to demo in whistler but you will end up paying. You can get 1.5 hours for free on any demo ski on the mountain but you will have to return them after 90 min or they will charge you.
you could rent skis, we have all this years salomon skis to try, its $50 a day, which is about what you will pay any where in town to demo.