Terminal 21 is ok if you know a quiet place to talk. Many places at Terminal 21 are busy and loud, so it might be hard to practice a foreign language. I can meet for lunch most days.
Central Embassy Starbucks (right off Phleon Chit) is quiet. Since it is a new mall, most restaurants are quiet too. I can also transfer to a place near the MRT if you prefer.
I'm an American diplomat with USAID. I provide economic advice to countries in the region to reduce poverty and protect the environment.