It seems like an anachronism to have Taldan characters in this adventure path. Unless something has changed, the Taldan fleet which founded Amanandar are first landing in Tian Xian around around the same time that this adventure path is starting. Did I miss something?
New Oppara was founded the same year the AP takes place. It's really not a surprise that someone may have decided to walk to the place right next door.
Like others have said, Amanandar was established the year that the AP takes place and is still a very young nation, but nevertheless exists. It's entirely concievable that some immigrants may have decided to set up shop in Shenmen. With Goka being such a big trading hub, it's also possible that a Taldane characters have originated from that part of Tian Xia.