I generally keep to myself when playing a casual round, often deep in thought and that might come across as being rude or unfriendly to people who don't know me. I'll occasionally join up with some newbs and try to offer some pointers if it seems like they are eager to learn but I usually only offer encouragement. Sometimes I've had people refuse my advice, acting like it was rude of me to suggest they try a different disc or change their stance a little. So it goes.
If someone wants help and asks I'm more than happy to assist, but generally I'd rather just do my thing and keep to myself.
I guess what I'm saying is don't be afraid to talk to people but I hope you don't assume that all people are unapproachable if they don't talk to you first.