Zoomom,
Cursillo is not really all that secret. It is a three day retreat that helps Catholic renew there Baptismal commitment to bring Christ to the world. It is Evangelical but it is not Charismatic. Those who have been through the "short course in Christianity" are encouraged to find others in there parish who they think would benefit from it. The candidate is not told alot about the weekend beforehand, but it is safe to say it is faithful to the Church and what it teaches.
It is amazing to see cradle Catholics (men in my case) who some for the first time have a deeply spiritual experience. There are small group sharing session. But if you are uncomfortable you do not have to contribute. It will renew your faith in Christ and the Church. All I can say is GO, if you get the chance.