Via Puffy's Japanese site and Twitter feed they have announced they will be at Comic-Con International: San Diego. Not much useful information on Puffy.jp but comingsoon.net gave a lot of details. Ami and Yumi are scheduled to appear on a panel for the the Teen Titans series on Sunday July 27th from 11:45 to 12:45. I would wager that someone will record this and hopefully do a post up. A full episode of Teen Titans will be shown, so that probably limits the panel to about 40 minutes and I am not certain how Puffy will fit into that.
It is encouraging Puffy will be making an appearance in the US, but this might be a very small window of opportunity for Puffy fans that happen to be in San Diego. So if you are there, please see them and report back!