Good point, bluemagic. Perhaps it is more common in certain locations. I have heard about difficulties finding testing sites, too.
I don't know about homeschoolers, but for kids enrolled in our hs, all you have to do is sign up for the exam (online) and the school will order the exam and give it. You do have to attend one of their per-administrations sessions, but that takes just a few minutes. Our guidance counselor suggested it is not uncommon for kids here to take some APs this way. The school does offer a fair number, but many kids' schedules are pretty packed, and I suspect it is a way to fit in more than the typical schedule allows.
I imagine it is also a good way to extend the curriculum in a less rigorous class- DD is planning on going this route in some classes, studying additional material with the goal of taking the AP exam if she feels she has adequate preparation. (She has found herself studying additional material anyway beyond the scope of her honors courses, just out of curiosity and need for knowledge, so this probably won't be a stretch, and if she find she hasn't had time or the inclination, she doesn't have to take the exam).
