I would like to make an appointment. Perroflauta came as it has said before, from poor people who lived in the street, usually with a dog, and they could be either playing music to get money or just like playing music in the street with theis fellows (perro=dog, flauta=flute). An example will be pretty helpful: in the simpsons, the chapter when lisa and other workers of the nuclear central start singing against mr burns. This may well remind us to hippies, as many people has said. Perroflautas concept has evolved from that to people who (nowadays) are kindda bohemians, who don't like following traditional streams. The oposite to a perroflauta would be queen elizabeth ii. Perroflautas are alternative people and this term may be used in a despective way on antisystems or radicals, but that does not mean that all perroflautas are radicals. Currently a perroflauta is someone just off the beaten track. They can be more or less radicals, more or less hippie-styled, etc.
It normally has a negative connotation because of its origin, but that doesn't mean perroflautas are vagabons, drug dealers and that stuff.
Important: this is my perception as a 19 year old man of Sevilla, south of Spain so i may see perroflauta in a different way! Slang and new idioms are not strict sticks but an undetermined concept.
As Ortega y Gasset said: everybody get a perception of a truth, so the sum of the perceptions might well get us closer to the truth!