I'll admit, the first time I had sex with a girl on her period kinda freaked me out. I didn't know it was 'that time' so I was a bit shocked when I saw 'ketchup on my hot dog'. She had to convince me that she was okay and then I slowly calmed down.
From my experience, girls do tend to be hornier around this time. I am not one to turn a lady down so I keep my eyes over the horizon and keep a towel nearby. Sure, it's a little gross but so worth it.
I've also been with a couple of girls who don't like to have sex during this time. Who am I to turn down a weeks worth of blowjobs?