The other thing to consider, though you're probably aware of this, is just how difficult it is for an outsider (a gaijin) to feel a part of a Japanese group. It took me a long time at my dojo to feel accepted--by my dojo-mates mostly, not by my teacher who welcomed me immediately. I think the more Japanese you know, the better your chances of fitting in.
My experience has been that I've been made feel as welcome and as "part of the group" as any Japanese beginner in the Dojo.
Most Japanese treat outsiders very well! Pretty much anyone joining a Dojo here is "soto" or "outside" for an inderterminate length of time until they be come "Uchi" or "inside". But isn't this true of Dojo everywhere? The Japanese are just more up front and formalised about it.
I think that the "outsiderness" many non Japanese feel in Dojos here is a two way street. Initially some Japanese may feel a little awkward dealing with a non Japanese speaking foreigner, but I think a lot of us (myself included) tend to be over sensitive to this, probably beacause we are in a completely different environment. (that and the small matter of the language...)
This is turning into a good list. Not too many Japan based people
regularly post for some reason.