well there are a lot of dedicated journals, i commend you just a couple: journal of ethnopharmacology (elsevier), Journal of Ethnobiology and Ethnomedicine (BMC)
Journal of ethnopharmacology does not require any publishing fee: http://www.journals.elsevier.com/journal-of-ethnopharmacology/. anyway me too i am writing a paper on ethnopharmacology, so you need assistance/help just send me a message