So low level, Limsa is tops(though gridania ul dah and the gold saucer are often populated as well). Im never surprised to bump into a few people when i poke my head into Revanents Toll. Foundation you should see a few more. Idyllshire is rarely empty of my server. Then you get to the current content, and Rhalgrs and Kugane are where you see a lot of people spend their "downtime"(emphasis on "see" because people who head off to instanced housing and the like cant really be seen). If you want to bump into people outside of town, check Quarrymill(south shroud) and later on Crick(ruby sea). You can only que for PotD/HoH if youre nearby, so the area arround each will typically be a populated one. If you want to see people out in the field fighting things together, Eureka has that. Heaviest when the instances are introduced of course. But just some random guys near the ceruleum processing plant in northern thanalan(to pick one out of the way location)? Kinda rare.