There is some truth in the Cocoa Mulch as being dangerous, but this was taken off the market years ago. For more information read this:
snopes.com: Cocoa Mulch Danger to Dogs. Also, ingesting chocolate isn't really as dangerous as some would have you believe, it's the dark chocolate that is dangerous because it has more Theobromine. For example, one chocolate kiss won't cause a problem but if they eat 1 ounce of chocolate per pound of body weight, rush them to a vet. Also, once they’ve had a taste of chocolate, they will seek it out.