Them beasts would eat you for lunch azzend first.
Polar bear would for sure. Grizzly's only if it were hungry. Black bears unlikely.
Black bears are much like dogs in that they have hierarchy and ettiquette rules. Both black and grizzly bears are very sensitive creatures and respond as such.
I am an animal lover. I have had the pleasure of visiting Coola and Grinder (resident grizzlies) up on Grouse Mountain. I have had the pleausure of watching a black bear walk from Burnaby Lake across our path. We were far enough away to be completely safe and it was an awesome experience. The bear knew we were there and didn't really care. He was calm and munching on the clover at the side of the trail by the time I'd had my visual fill.
I've never had any personal experience with polar bears, but I know of a trainer in Abbotsford (couple of miles down the road from me) whom has a polar bear friend. I sure would love to see his bears in person. It would be a dream come true.