In pre and post season tournaments, usually it is unavoidable to have contact with coaches. In fact, lots of times a coach is the sponsor and arranges for your payment, sometimes at the gym on game day. How are you not going to talk to him/her in that case?
I never have had any problem chatting with coaches in these situations. I have known most of them for years, and they all realize that regardless of how friendly we are off the court, it has no bearing on my calls on the court. If they ever forget this, they are reminded of it the first time they complain
I am on the Board of our local youth organization and since we have a competitive division as well as a rec division, I am in frequent contact with our boys and girls high school coaches. I do a summer league for the girls coach and his school is represented in the league. He knows full well that we are friends off the court, but on the court I am all business. If you establish this early on, you should not have any trouble. However, if you are relatively new, my advice is to keep it brief and pleasant to all coaches off the court - probably no more than general greetings.