While it is currently undergoing some OOC transition (I’m not aware of the details) Jadepaw Dynasty is another long-established guild on the Alliance side.
It’s worth mentioning that many of us - as individuals and as groups - are IC non-aligned. We identify as Pandaren first, and emphasize participation in neutral events. Regardless of where you find a home guild, you’ll still be able to interact with all the guilds mentioned.