I am having the same issue. The regular WordPress search box will not display any content from my Groups page. I think it is hilarious that when I go to create a group, under settings the public and private options say that group content will show up in search results. I have tried relevanssi and that didn’t help.
I was looking for something similar, only I want to put in a description on my registration page. Just a paragraph explaining a couple of things at the registration page. I can’t believe that this would be a plugin not a feature with buddypress. If this is operator error (which I think is most likely) then please tell me how to do this.