“And since a woman’s the best there is […] I want to be one.” 

Molina is explaining what others tell him: that homosexuals can straighten themselves out and the way to ‘cure’ his sexual inclinations is to get a woman. However,Molina feels as though he is a woman and wishes that he could be with a man.

“I don’t believe in that business of living for the moment, Molina, nobody lives for the moment. That’s Garden of Eden stuff.”

Molina tells Valentin to “live in the moment,” but Valentin is determined to focus on the future, especially as it relates to the political revolution. He implies that living for the moment is unrealistic, and a form of escapism.

Social revolution, that’s what’s important, and gratifying the sense is only secondary. While the struggle goes on, and [will probably] go on for the rest of my life, it’s not right for me to cultivate any kind of sensual gratification […] the greatest pleasure [is] […] knowing I’ve put myself in the service of what’s truly noble […] and I can get that pleasure anywhere, right here in this cell, even in torture.” 

Valentin is explaining to Molina that social revolution comes before anything else, including sexual gratification. He believes that storytelling, which helps Molina mentally escape the cell, is dangerous, and like a drug. Instead of fantasizing, Valentin suggests that studying philosophy every day helps him escape the cell and continue his fight in the revolution.