Hi!
I've registered and edited on several Wikipedias where I don't speak the language; I've managed to work everything out based on the the location and URLs of the links.
We all can do it... personally I'll probably never need anything else that en:wiki+commons+meta. The problem is a full user base, not people having an EN-e plus a good practice in using wikies and comps and pending a number of hours a day inside a wiki... I'm not staying up all night to serve just 30 people. I want people who are not net-junkies to be able to use it, too. :) If we cannot manage to present occasional users with easy tools we loose traffic. Not a big deal for ES.wiki, as they got billions of possible users, but really something to be avoided in our situation.
Maybe the local links to Commons could have "?uselang=" at the end of the URLs?
Yes! http://commons.wikimedia.org/?uselang=fr works. Is it an acceptable practice? By the way... this thing alone would have interwiki links mantain a stable interface, if put on the main soft engine... I do not really think that it would cost much work...
This is not what I want, but it's better than nothing. The good thing would be a dedicated page there, that would upload images to commons, as the old one did. Any time you ask a user to click once more you loose traffic. Things must be as simple as possible.
Bèrto