Hampyeong Butterfly Festival (함평나비대축제) in Hampyeong country through May 10th. One of the region's better-known festivals, it's essentially a nice walk through a big park, I concluded during a 2009 visit it's somewhat lacking in butterflies in a natural setting (at least for those who come from places with abundant nature). A short walk from the bus terminal in Hampyeong-eup, in turn accessible by regular buses from Gwangju. Times available from the Gwangju U-Square terminal website, in Korean.
Damyang Bamboo Festival (담양대나무축제) in Damyang county from May 3rd through May 8th. One of the province's representative sites, it's a short bus ride from Gwangju. Worth a visit anytime during the spring and summer months, the festival offers the usual, um, festivities.
Shinan Heuksan Skate Festival (산안흑산홍어축제) on May 6th and 7th. One of the two big hongeo festivals in Jeollanam-do celebrating the region's affinity for the acquired taste of fermented skate. Somewhat out of the way on Heuksan-do, one of the 1,004 islands that comprise Shinan county, those with time and an interest in seeing an even more remote part of Jeollanam-do would probably enjoy the trip.
Jeamsan Azalea Festival (제암산철쭉제) on Mt. Jeam in Jangheung county on May 8th.
Seomjin River Azalea Festival (섬진강 철길 철쭉축제) in Gokseong county on May 7th and 8th.
Boseong Green Tea Festival (보성녹차대축제) in Boseong county from May 4th through the 8th. The tea fields in Boseong have provided this blog's header for years, and the area is worth a visit for anyone living, um, in the area. It offers the usual stuff, plus green tea samgyeopsal, green tea noodles, green tea ice cream, and green tea green tea. Buses run regularly to the main field from the terminal in Boseong-eup, and there is a small entrance fee.
Suncheon Nagan Folk Culture Festival (순천낙안민속문화축제) in Suncheon's Nagan Folk Village from May 13th through the 15th. In one of my favorite places in Jeollanam-do, here are some posts and pictures from previous years: from May 2008, October 2008, and an unblogged set from May 2009. The folk village is accessible from downtown Suncheon via city buses 61 and 63 (timetable, in Korean), and when you get off at the village you'll find a timetable for buses returning to town.