http://www.mayfest.org/festival-guide#faq
Question 14....
They have been posted in the past.Prohibited:
Coolers of any kind (except for medical use)
Illegal drugs and drug paraphernalia
Pets (except for clearly marked service animals)
Outside food or beverages
Skateboards, scooters, or bikes. If you ride your bike to Mayfest, free parking is available at the south entrance gate.
Unauthorized materials including flyers, stickers, samples, etc.
Weapons or explosives of any kind
No open carry of handguns. No concealed carry of handguns.