What language should I speak?

I'm kind of in a pensive mood since yesterday.
I do a language exchange every Wednesday, so we gathered yesterday as usual.
Since it has been chilly, some wanted to have a lesson inside rather than at the park where we usually do. The confusion had started. We tried the community center near Christie subway station and were told that we were not supposed to have a lesson there. One member offered one restaurant which is less busy that time of day. We walked there rather long time but there wasn't enough space for us. We tried one of bars near there afterward and asked the owner to keep the music down, but he told us that he didn't want to do it because he wants to keep their atmosphere as usual. After wandering for 30 mins, two people took off. We decided to just have dinner and talk about the place for the next time. We got two new people but they were headed home after short staying at the restaurant. I felt sorry for them. Anyway, I wasn't in a good mood but practically as a leader of that meeting, I couldn't express my feeling directly. I hid my feeling and I was heading the place where one offered to check out for the next meeting. He is a Korean and wanted to speak English with me, so we were talking in English, then I got an unexpected call from my friend, who is a landed immigrant from Korea and I talk with him in Korean, actually he is the only person I speak Korean with. I had spoken in English all day long, so I started talking English with him simultaniously over the phone and a moment later, I realized we speak Korean each other but I though it wasn't a big deal speaking English even though he spoke to me in Korean. He wanted to hang out with us. So, I just wanted to let him know that I was with someone who is Korean but we had been speaking English and if we speak Korean, it might have been awkward. But on the way to the place we were going to meet, I talked to the guy that I and my friend talk in Korean, so if he wants to speak Korean, we should speak Korean.
As we got there, I got very angry and sarcastic reaction from my friend. He talked to me in Korean that he got pissed off because I kept speaking English during the call and he might have to speak English with us. He thought I intended to avoid him and that's why I spoke to him in English. I was just a bit disappointed about his reaction at first but tried to calm down myself and explained what we were talking about on the way there.
As an international student, we are here to learn a new language and trying to speak a target language as much as possible even with Korean speakers, Time is limited for us, I don't have many close korean friends here, anyway. Yesterday's is very rare occasion for me. However, for him, he is a landed immigrant, he's not serious about a language; he always speak Korean to us without any consideration which I found it a little annoying. He has a plenty of time to pick up a language unlike us. He may not notice about this and has a different standard of it.
Anyway, I hid my upset feeling and had chatting with them for two hours, trying to make it up. When I got home, I was so stressed out and depressed about what I experienced before. I have no idea how I can handle that situation. I guess it would be better to speak Korean with Koreans. I don't have many chance to hang out with them anyway.
Did I make a mistake or that is just the thing every student face with every day.
Spending time with Korean is the most challenging thing here which seems to sound
weird because I am Korean and like Korean.
It is time to throw my skates on and forget about it.