By all means pop in and say a quick hello and brief chat. But be aware that they crew have lots of little duties to do and do not become a hinderence. A few minutes is more then enough unless it is actually the crew member who is engaging you in conversation (because if its the other way they are perhaps just being polite by not telling you to leave) and DO NOT lecture to any crew member for 40 minutes all the reasons why my airline is worse then the rest!!!! Just had it about 4 hours ago and my gawd I was ready for blood!!!!