My oldest daughter had/has one on the side of chin area and extending down her neck. She also had it on her bottom lip. When she was 3 months old it suddenly swelled and made the whole side of face look very swollen. We did the CT scan to make sure if it was interfering with the nerves in her face. Since it wasn't, we elected not to pursue surgery at that point. She is now seven and the spots have diminished to looking more like a light rash than a birthmark. The swelling she had took a little over 4 months to go away.
We did get lots of comments from people- not all were bad. Some were from others whose kids had gone through the same thing. Others were much less PC. We heard everything from her being burned, to asking if she had spilled jello on her, or marked herself with markers.
She took it all in stride, which helped me out tremendously. By the time she could talk good she would straight up tell people, NO, it's my birthmark. By age 3 the brightness had really gotten less, and now noone even notices. Our doctor had told us that it would more than likely dissapear by 1st grade, and it pretty much has. I also never heard any of her friends or classmates pick on her for it. That was a huge relief. I also understand that there are situations that require the surgery to take place. Best of luck with whatever you decide to go through with. Overall I would say the comments were few and far between over the years, and I never really caught anyone staring. Good Luck!