They're holding it on June 18th, so you have plenty of time to pack your picnic lunch and get there early for a good spot. I suggest setting up your lawn chairs right next to one of the amplifiers so's you can fully bask in the Hollerin' Contest experience.
As the link above mentions, along with the contest there is an antique farm equipment exhibit, classic car show, corn hole tournament, concerts and naturally food vendors. I'm guessing the food alone would make the trip worth it. Visit their 43rd Annual Hollerin' Contest webpage for driving directions to the contest.