I've heard honey is good for diabetic wounds is this true or a myth?

Multiple factors. Honey is a small aspect of the larger picture. Wound care requires multi-discipline input for proper wound healing. There are multiple modalities and multiple strategies to get a wound closed but it takes a knowledgeable well trained specialist to know when to implement the appropriate treatment during the course of wound healing using evidence based medicine.
Not so simple. There is a form of sterile honey that is used as a wound dressing, and can improve healing in certain wounds. However, wound care is very complex, and saying that medical honey is good for all diabetic wounds is an oversimplification. If you have a diabetic wound it should really be evaluated by a wound specialist to determine what the best treatment is.
Maybe. Studies are coming about the the use of honey in wound healing. The major caveat being: this must only be used under the guidance and supervision of a trained medical professional that sees and treats wounds and must only be a medical grade product. A wound professional will determine if a wound is an appropriate candidate for this therapy.
It is true. There is medihoney which is used in the treatment of all wounds. It is only a part of the care though. See a wound care special that will evaluate the entire situation. Apligraf is another product commonly used in the treatment of diabetic wounds.
Medical grade honey. Medical grade honey has become a useful tool for wound care docs. It helps clean up wth wound and promote healing. It does depend on what is going on with the wound. As with anything good wound care is a must and it must be medical grade honey, not just commercial honey you use to eat.