In Lorelai's reference letter she states that she has known Luke Danes for almost 10 years. This is consistent with the fact that in season 5 episode "Written in the Stars" Luke told her he had met her eight years earlier. Also, in "Santa's Secret Stuff" Luke implies to April that he met Rory when he was her age. It seems unlikely that she didn't know Luke for the first eleven years she lived there. In Season 5, episode "Wedding Bell Blues", after the Luke/Christopher debacle Lorelai said to Rory that Luke still remembered her in angel wings. This implied that her knew her at a very young age...probably 5 or 6 or younger, not 11 or 12.