I don't think this should be a major concern for anyone going on the orientation course this week. It's not like we're short of opportunities to drink on any other day while teaching in Korea.
I'm not sure what the orientation will be like in Seoul, but during the EPIK orientation last month (with GEPIK teachers attending as well) they weren't very strict about the rules. There were a few of us who would leave during lunch to get something else instead of cafeteria food for lunch, some who'd go during dinner too. And in the evenings once classes were done, the majority of attendees would leave to drink or party off site. About 50% stuck to the curfew and others, occasionally myself included would come back at about 3 in the morning... without anyone kicking up a fuss.
Just be reasonable and don't give them a reason to be forced to "discipline" you.
I'm not saying use this as a guide for your actions, but consider that perhaps they will be flexible. Your not going off to a prison camp after all. It's just an opportunity for teachers to share ideas, maybe learn something new and perhaps make some friends. Enjoy it, the foods good for the most part, accommodation quite comfortable and it's a week away from school which you get payed for.