I had a difficult time clipping in with Candies on my mtb with the second foot only, but I think that was more b/c I was wearing the clunkier "hiking boot" type of mtb shoes. I shaved the tread down some but still had a difficult time clipping in, and that made riding rooty, rocky trails really frustrating as I'd often have to ride for quite awhile with one foot clipped out.

Because of all the great recommendations here, I switched to Speedplay Frog pedals and find them much easier to get into from any position. Sure, they're only two-sided, but one side is always "up", so there's never any thought to it. I changed shoes at the same time, so it may have been that the Candies would have been just fine with the new shoes.