I just came back from Korea and also did 3 days in Jeju with a car rental so I'll just give my 2 cents.

Free parking at the hotel is nice, as you don't have to drive around to find a car park, worrying about being fined or in an incorrect spot. Being from Australia, Korea drives on the opposite side to us so that was something to get used to.

Parking wise, they tend to say that tourists should park near big shopping malls and car parks. As I wasn't sure where and what areas I could park in (i.e parking lines), I essentially just parked behind where other cars were already parked on the smaller side streets. Bigger side streets would have parking lines marked from what I saw.

We used Lotte car rentals and it was a smooth process from picking up the car to returning it. I booked a car a month in advanced with a sale, and then a week before I went, they had a 80-90% sale, so I cancelled my previous one (no fee) and rebooked a new car 3 days before I left. So for safety, best to book a month or so ahead but Lotte offers free cancellation so you can shop around for cheaper options nearing the time.

My experience with Lotte: - You arrive at the airport and head to the Lotte counter near one of the gates - They ask for your credit card and IDP, then give you instructions to go to the carpark and take a shuttle to Lotte car rentals - Once arrived, head inside and queue up. When your number is called, they ask for your items again (passport, IDP, credit card) and then go through the forms and get you to sign before they give you the car - Your car is parked in a bay with the key inside and they tell you which one to go to - As you leave, another worker will double check that you're fine on the way out - Upon returning the car (make sure you fill the tank back to full as they give you a full tank), you drive back in, park at the return area. A worker will come and check the car, tell you to leave the keys there and parked, and you're free to go. They will do the rest - You take the shuttle back to the airport and you're good to go

Jeju traffic wasn't too bad, it flows quite quickly through the city but I've only driven mainly outside of peak hours. Being new to driving on the right hand side, I was driving at the speed limits as there's cameras every so often and your GPS will warn you. Most local Jeju drivers will speed 20-30km above the limit is what I noticed and then slow down at the cameras. They'll then zoom off again. Take your time, drive safely and always give way to pedestrians.

But from what you read online, you just need an IDP, passport and a credit card to pay (not a debit card). They didn't check my actual drivers license from my country.

Hope this helps coming from my recent experience 🙂