Don't cancel your contract.
Find out who the realtor is that has the listing. Then, write them a letter (mail it certified) telling them you have a contract to use that facility on a specific date, and you understand the property has been listed with them for sale. State that if there is an offer to purchase the property, prior to the date you've contracted to use the facility, you expect either the settlement of any such sale to be delayed, in order for the current owner to fulfill their legal/contractual responsibility to you, or for the purchaser of the facility to sign a legally binding document, prior to purchase, indicating they will honor your contract.
After you talk to the folks who sent you the letter from the venue, write them a letter reiterating everything they told you that wasn't already in writing, and send it certified.
I wouldn't scream or yell or otherwise make a big stink. But, I would put everything in writing to anyone that mattered, in case you have to sue them all in the end. Basically, if people are putting things in writing, they'll be sure not to screw you, because they'll know you're more than prepared to win in court.