Sorry, I can't help you by saying where to go for interaction on Excalibur, or even tell you which servers are more populated. But I do have a couple of tips:

1) Check out the forums for Excalibur here. Looks like there's at least one social LS recruiting here (Chocobo Feather). You can check out the posts on that forum while looking for others to play with. And you can post in there that you're looking for others to play with.

2) I'm not sure which city you're in now. But on most servers, most of the players have migrated to Uldah. So if you're looking for other people to interact with, it seems like going to Uldah might be your best bet.

Welcome to the game, and good luck!