Behind one of the booths sits anthropology professor Silvia Rivera Cusiqanqui, from the University of La Paz. She has written extensively on the role of coca in Bolivian culture. Her books are on display and for sale at the Coca Fair.
When she is asked about the worldwide perception that coca is the same as cocaine, she gets agitated. "You are wrong," she said. "This has such big medicinal value, and it's absolutely unfair and it's a campaign -- a dirty war -- against coca."
Bolivia's president agrees. "The is an unfair penalization of the coca leaf," Morales said. "We know scientifically that the coca leaf does not harm human beings."
This week in response to a U.N. report that criticized Bolivia's coca policy, Morales announced plans to spend $300,000 to develop legal markets for coca.
The United States has tried to entice coca farmers to abandon their crop and replace it with more conventional plants: coffee, bananas, for example. Representatives of U.S. AID took ABC News to a coffee farm that has imported high-quality coffee trees from Colombia -- with U.S. help -- and is now producing a profitable organic coffee bean that is sold in specialty stores in North America.
Coffee is far easier to grow but the family we met, with 50 acres, said it would be impossible to survive on coffee with the 2 acres that Emerjildo Chavez works with is family of five.
A single coffee crop brings in about as much as a single coca crop.
"There is a huge difference," Chavez said, "because coffee can only be harvested once a year, where coca may be harvested three or four times annually."
Chavez hopes the Bolivian president can convince the world that not all coca is bad. But that is a tall order.
"I don't believe the rest of the world will take a new look at coca as product," said Philip Goldberg, U.S. ambassador to Bolivia, "I think what we need to do is to control coca and try to reduce cocaine manufacture. Whether we like it or not, the majority of coca that is grown in Bolivia and in other countries goes to the illicit, illegal manufacture of drugs."
Emerjildo Chavez sees it very differently. "Coca is a gift for us," he said. "I'm proud of our president for standing up to the United States."