B.C.
A guy asked me out once when my 1st DD was 2 months old. My hormonal response? "As long as you have a safe car to drive b/c I have a newborn!" Lol. He left me alone after that, even though I was totally willing. ;)
When I started dating my husband he already knew I had a child, and I held nothing back when he wanted to date me. We had talked for a few times and I basically laid it out as "You know that I have Julia and she comes first. I'd love to date you, but you have to realize that we a package deal." That was 10 years ago, so my advice is, let them know! The right guy won't let that hold him back from you.