In the six years that Nick Schroth has been making the 500-mile round trip from Palisade to the Front Range to sell produce at farmers markets, he has never seen a dog bite anyone and never heard a complaint from other vendors or customers. “A lot of people enjoy seeing them out here,” Schroth, 33, said at a recent City Park Esplanade Fresh Market on East Colfax Avenue, where at least a dozen leashed pooches browsed with their owners.