this sounds a lot like where i live. here in iowa there are no mountains either but we've got the bluffs that run along pretty much the entire missouri river. ive never really tried looking for herps in there but i imagine there would only be some snakes.
im not sure of any herp societies around me, there may be some in des moines or omaha, idk if they have group meetings but the nabraska herp society is the one that puts on the herp show twice a year. ill have to look into these and see if i could go to one. thnx for the idea