Hello Nancy,
I studied French in high school and in college, but like Dawn, I don't speak it very well anymore due to lack of use. Many scientific meetings, even ones in foreign countries, are conducted in English. I've attended three conferences in France, and every one was conducted in English. I think the reason is that these meetings are attended by scientists from around the world, who are native speakers of many different languages - English, Chinese, Japanese, Russian, French, German, Swedish, and Spanish, to name a few. Many people around the world study English in school, so that seems to be a language we all can speak in common at an international conference. Many scientific journals also publish their papers in English - even ones based in Europe!
However, there are situations where speaking a foreign languages can be very useful. Having skills in a foreign languange can be helpful when traveling to conferences, especially when the meeting is in a remote location that requires you to drive or take a train from the airport. After completing their Ph.D. degrees, some young scientists do post-doctoral research in a foreign country for a year or two. If you are going to live and work in another country, in certainly helps to be able to speak and write their language!
Kris