I'm pretty sure this one is located in front of the Gangjin County Office, and I know there's at least one more placard in town, and perhaps their locations correspond to the points on the crude map. I remember seeing another placard beside the old bus terminal, and you can see it next to the new one in this photograph.
The English text on the picture I've included reads:
May 18 Kwangju Demonstration Movement.
The Demonstration Movement in Kangjin area has been ignited by demonstrators arrived in Kangjin from Kwangju City by eight buses on May 21, 1980.
As the demonstrators entered the Kangjin, the police forces voluntarily withdrew their forces avoiding physical clash. Citizens being already aware of the Kwangju massacre welcomed the student demonstrators and joined with them.
Having set up their headquarter at the Kangjin church, the students and citizens made an organized demonstration in several places such as County Hall and Bus Terminal. At night, they stayed at the church or the inns nearby and the sisters from the church offered foods to them.
On May 23, 1980, about 500 students from Kangjin Agricultural High School gathered together and joined in the demonstration screaming "Lift the Martial Law", "Recover the democracy", and "Free Kim Dae Jung". The demonstration reached its climax as the members from the Regional Young Man's Association and Young Man's Counsel add to the demonstration group. On May 23rd, there were two bullet wounded people and many other wounded ones from Haenam Wooseljae clash against the Martial Law Command and they were hospitalized and cared for in the provincial hospital, the current Kangjin clinic.
On May 24th, Civilian Force and students joined together and made their last demonstration as they approached to Jangheung area during which no wounded ones occurred.