Question: do girls talk about their boyfriend's penis sizes? 

Answer: Girls probably talk a lot more than guys do when it comes to relationships. That's just the way it is. And when you put women together they can talk about almost anything because that is the way we connect to each other. Plus we like to talk a lot in general. So, to answer your question, "yes", if it comes up in conversation about penis size then women will talk about it; just as if "what type of laundry detergent do you use" will also spark the same type of conversation. Basically we will talk about anything!
This question from the Yahoo Q&A forum is categorized in the topic: Family & Relationships