Hi David, probably the Dharma Bums (Bagabundos de Darma- read it in spanish), of course On the Road, but Dharma Bums is more spiritual. The first one of Kerouac The Town and the City is also a great book, but less of a beat piece
Mind Breaths by Ginsberg is pretty solid. I love that he portrays himself as so many different things. It shows how impossible it is to completely capture a person with words.