Jinju-si is quite a small town with not much to see. The main attractions are the Jinju Fortress (Castle) and the festivals.
So I recommend visiting when a festival is going on (either the bullfighting festival or the lantern festival in early October. Day trip.
Jinju is a small, quaint city in South Gyengsan province in Korea. Probably the most beautiful city in all of Korea.
Superb cherry blossoms, superb lantern festival, superb old fort stooped in history.
Very pleasant and warm city. Since this city is several hours South of Seoul, the city is much warmer than Seoul.
Also, areas surround Jinju are mountainous, so air here is really clean and refreshing. There are historical landmarks to see along with lots of mountains for back packing or hiking. Every year they have a Natural/Herbal Medicine festival which was a wonderful experience to part take. Overall, Jinju is a beautiful city. Oh, and don't forget to visit Jinju Castle, which is one of the major attractions in Jinju. Can't wait to go visit again!
As above, not really there long enough to form a proper opinion. Seemed OK and not able to say much more.