Well, I'd suggest you talk to the person in charge of recruiting to figure out how are things going in the FC
As FC leader myself, I'd say I wouldn't mind much about people getting in and out, as long as they talk to me and tell me why would they quit.
I've encountered a lot of people who jumped in, made friends, had fun and left after knowing what kind of FC suits their playstyle and their need.
So, like Kata said, don't be afraid, nice people will stay friends even you left for better/more suitable FC.