Will it be in English or French? And will it be under 21 friendly? I'll be visiting Paris at that time (I'm living in Madison, Wisconsin), and would love to stop by.
I'm hoping to attend and my French is quite rustic (i.e. horrible), so that is at least one non-French speaker for you. As to the age thing: here in Europe, nobody will check your age when you enter a bar. If you look particularly young they might not let you order personally, but they would probably serve beer to a 12 year old if one of his parents would order it for him. I'm not sure how old you are, but I think the legal drinking age in most European countries is 16 (and 18 for strong liquor).
It's hard to tell. Sometimes, French people are very conservative about which language to use. But I'm sure every attendees will speak English fluently.
Do not hesitate to contact us before the event if you want more information.