Sparkly: “can you say hi to a guy that your family friends with at college?”
Sparkly, as I wrote in my above response to yekke2, it is best to find someone (preferably a female) to discuss these issues with in person since they are not “yes and no”, “black and white” issues, and they do involve a discussion and not a yes or no answer.
If you don’t have someone to discuss it with, my personal opinion is that you should not refrain from ever speaking to members of the other gender (saying hello to a family friend is appropriate), BUT you should try to work on establishing more boundaries for yourself (this could be a matter of not being friends with guys who are not shomer negiah, or not having guys in your apartment, for examples).
That’s just my opinion – take it or leave it.