I think it would be hypocritical to limit use of this project to only English speakers. In this category it’s ok to speak your native language. I know most people who can will use English anyway as it is the most common language, but if you need to use a different language to ask or answer a question, please do. The rest of us know how to use the internet to look up translations.
One thing I would suggest is that as we get groups of people learning the same language, I’ll create sub-categories for those languages. Please try to stick to posting in that language in those subcategories. Of course it’s ok to bend the rule. Let’s say I’m asking a question in French in a Francais sub-category. It might make sense for someone to answer my question in English to give me a better understanding. It’s totally cool to help each other out in whichever language achieves it best!