What I know of of existing Pandaren themed guilds currently active on Alliance side there’s:
The Fallen Leaf (as already mentioned) and Yu Xin Keepers
The guild I am currently in is also Pandaren themed but dormant, I am about to seek membership of Yu Xin Keepers though, the smallest of the mentioned guilds, as their cause matches something Qufu could back 100% up on closest.
Both guilds have guild threads here on the forum, and Argent Archive pages as well.
Here’s the link to the Yu Xin Keepers guild thread: [Pandaren A/N RP] Yu Xin Keepers
Edit: Edited out The Wun Dynasty as I was informed they are dormant.