I don't know of an easy workaround for this, but gut feeling tells me you should keep globalization enabled (with only 1 language enabled for each site) and - if necessary - find another way to hide the language selectors.
If you are using CMS 6 and you have different editors for different languages, perhaps you can use the new language "access rights" in combination with Teds suggestion to hide the languages you don't want visible to that editor?
I'm currently working on a project where I set up two enterprise sites, each with a different default language on the start page and then turned the globalization off.
The requested functionality is hiding the language selectors and only allowing the editors to create a page on a specific language under a certain site.
The problem is that when you enter the edit mode from either site, that site’s content language seems to get set for the other site as well. So when trying to edit a page on the other site it assumes the first site’s language and since globalization is turned off, there’s no way for the editor to change language.
So, what’s setting the language? A cookie? And how can I override this behavior?