Anytime before you make the invitations so people know where to shop.
Im 20wks and registered last week. My baby shower is in June as well:)
im 26+5 and did mine about 2 weeks ago.. just didn't tell anyone til my mom sends my invites out.. you can do it whenever you want!
Thanks ladies!!!! Might do it in the next cpl wks :)
Do it when you find out what you're having