from the fAQs i gather that it sends from one gotenna to one or more recipient gotennas only: "Your smartphone will send the message to your goTenna, which will then shoot it out, via long-range radio waves, to the intended goTenna(s). At the other end, the exact same thing happens, in reverse: the recipient goTenna sends your message over BTLE to the smartphone app its paired with."

https://gotenna.myshopify.com/pages/faqs

building an ad-hoc network with these things would be kind of cool though. DIY city networks anyone...