You're going an awful long way to go to a new venue... perhaps you should try another town in Europe where people could at least understand what you say?
If you're considering a street show, you might want to ask whether you need any special permits? It'd be an awful shock if you set up shop only to get fined or hauled away by the police.
As for a lively area, perhaps one of the parks, or Ueno, Asakusa, Shibuya, Shinjuku or Harajuku. Roppongi has a lot of foreigners and might also be a good place to consider, but until you have some REAL plans (and at least one Japanese friend to show you around) I'd consider a country where German is a common language.