When should you go to Buenos Aires?I would say: as soon as possible. Go before it’s too late! You will gain nothing by waiting. You will not be good enough, anyway ;-) But do by all means go!
If you wait until you are ready, you risk missing out on the entire thing. Going to milongas in your neighborhood, you will believe you improve to become a good dancer, and that you know what tango is about. If you do, and then go to Buenos Aires, you will have to take the lesson. You will not be the best dancer by far. You will have to work to get dances. But it will be worth it. If you go earlier, chances are you are more humble, and get more out of the experience.
Besides, to really get the tango, you have to breathe the air of the city, watch the porteños walk by in the streets, hear your neighbours play tango music and discuss music and life with the taxi drivers on your way to the milongas.
Of course, this is based on observations of an extremely small sample of people, but I think i makes sense :-)
So order these tickets, the sooner the better.
I remember reading a post about the benefits of going over at Alex Fuego earlier, go there as well..