Actually Facebook allows you to set the information that is available to others. Like address, location and such the individual has control of and can be visible only one person (me only) for things like address.
Your public profile can be set https://www.facebook.com/help/325807937506242
Anyone from a group not directly linked to you a a friend can only visit your public profile and see what you've permitted the world to see. Which may be accessible to search engines outside of Facebook, it depends on your setting. So no member of the group has access to more information than you're already freely sharing with search engines.
The above link explains a bit more how to make your Facebook more private. If it is a concern.