Are girls sexually attracted to penises?

That depends on the woman. Women have sexual desires and needs just like a man. Straight women would desire the penetration as well as the other aspects of a sexual relationship, which does include a male penis.

Every woman is different and desire different things, but yes, some women do have sexual desires for a man's penis. Just like straight men have the desire for a woman or gay men may have the desire for a male penis, or a gay woman has the desire for another woman.