Before you come down to the shore in Sept make sure you check the dates of the seasons - the only thing you can shoot in Sept to my knowledge is Canada Geese and seaducks after Sept 24th. We don't have early teal season here in NJ.
To answer your question teals are not that thick along the coastal region, although they are here you are much better off going to the Delaware Bay side as they prefer the brackish/fresh water marshes over there. They are found up the rivers on the ocean side where the water is more brackish, but they are thick on the Delaware side. The southern season opens Oct 19th.
“The perils of duck hunting are great- especially for the duck” Walter Cronkite