Ah, we just wanted to make learning Design Patterns fun. It's up to you if you choose to use them or not. I do think that having some knowledge about patterns and principles can help you. And of course we put in the disclaimers about over-reliance on patterns, we put it at the end so as not to discourage people before they even start!
Regarding the cover: we wanted to make design patterns accessible to women and show that women can code too. This is not a "sexual" cover, it's a strong, fun woman. At least that's the way I see it (as a woman). But obviously everyone will have their own opinion about that.
Sorry you didn't like it! Head First is definitely not for everyone.