If I was attacked on home depot property and one of their fence posts was made available to use as a weapon do I have grounds to sue Home Depot?

As a general rule, the attacker is responsible for this assault and battery.  The only way you can argue liability on the part of Home Depot is if they are responsible in some way.  If this attacker was known to frequent the area and Home Depot was aware prior, perhaps the company could have done something to prevent this.  Otherwise, I don't see this as a foreseeable event where precautions should have been made prior to the attack.  I am very sorry to hear about what happened to you.  My best suggestion is to speak with the DA's office that is handling the criminal matter (if there is one) and see if you can seek restitution from the offending party.  Best of luck.