Can you block people from viewing what groups you join on facebook?

[Krystabelle]

[Simi]

Yes, you can hide groups from your friends or from limited group of persons or you can keep the settings up to you only but it will hide all groups not selected or few groups, For this :
At the top right corner Click on > Accounts > Application Settings > if you view the list by scrolling a bit down, you'll find "Groups" Click on Edit Settings at the right side in the same row, In that, under Profile tab, you'll find Privacy > Select "Only Friends" or "Friends of Freinds" or In "Customize", select "Only Me" or type the names of friends to whom you want to share groups.

Plz Note: With this you will hide all of your groups.

Hope it Helps...