That would be more like "Hey everyone, I'm George". Humans also 'encode' information in that sense - from that introduction you could probably tell age, general health and friendliness.
The day we can talk to any stranger dolphin and have a real conversation will be alike to contacting alien life.
Actually, I don't think it will be all that alien. The conversation will probably be quite understandable. You will get conversations about fishing, who's pregnant, who you want to make pregnant, how your kids are doing, the temperature of the water, where the predators are. They probably tell stories, but they will be quite understandable to us. Fundamentally it's because the basic constraints of their lives are just like ours: get raised by mom, have friends, learn to hunt, mate, avoid predators and have fun while you can!