Cute pics! My DS's hair looks a lot like your son's. It was a couple inches longer but then he asked for a haircut. (I always said I'd cut it when he asked, but was so bummed that he wasn't even 2yrs old when he did ask! But I just trimmed it a bit & he was happy, and we'll let it grow until he asks again.)
Anyway, yes, my DS is almost always mistaken for a girl (even when he's wearing typical 'boy' clothes)... I don't even bother correcting them unless it's someone we're likely to see again. It's the hair, apparently, according to what people have told me. Also if I put him in pigtails, he looks like a girl even to me, so maybe it's his baby face too. Oh well. I don't care, but I did care when an uncle who hadn't seen DS in a while sarcastically said, "Who's this GIRL? Tell Mommy to cut your hair so you can look like a boy."