You’ve probably already found an answer to your original question, but if it helps anyone else, I’ve done exactly that using q-translate as a plugin.
Despite the name of the software, it doesn’t actually translate anything. What it does is set up the backend so that when you enter a post your first language, you can then click a tab to do the same post in a second language. It does the same for the menus. What it basically does is make sure that each part of the page has a corresponding element in each language. But you have to enter the copy twice (which is good, because you want it to be written properly).
If a post or page only exists in one language, you can choose to have it not appear at all on the second language pages, or it can appear in its original language.
I live in Finland but am constantly doing sites where both English and Finnish are of equal importance. I found q-translate to be the easiest way to work this out. The only thing you have to keep an eye out for is if WP does a big fat update and your plugin isn’t ready for it yet. Q-t seems to be one of those that is updated quickly enough that you don’t have any problems.
