My husband brings his DSLR (Nikon D300S) every year to HHN. You cannot take pics in the houses, but can get some great shots in the streets.
Our advice is to make sure you bring your lens cap. Keep it in your pocket while in the streets. Put the camera around your neck and put the lens cap on while in line waiting for the houses so it is clear to the workers when you're entering the house that you will abide by the rules. While in the house, keep the camera to your side or behind you (slung over your shoulder) - some of the houses spray you with some water - not sure if this will happen this year. This way your camera stays dry. We don't ever bother with the case - it is too big and bulky. We keep a plastic shopping bag in our pocket in case it rains, but only had to use that once. You could always get one from the gift shop, too. You'll have to use a free locker if you want to ride The Mummy or Rip Ride and Rockit.
The streets are dimly lit and a lens with a good focal length is preferred. But, you'll definitely need something that's rather fast or knowledge of how to use your advanced manual settings. That will lend to the best pictures with lighting movement, etc. My husband has brought a speed light in the past. It's takes nice pictures but is a BIG PAIN to carry around, so really it was more trouble than it was worth.
We have ALWAYS found that the scare actors will pose for a picture as long as we ask politely. In fact, a lot of them actually pose or ham it up without us asking. I think that they sometimes think those with the more professional-looking camera may be from a website or blog and want to show off their awesome SFX makeup.
The key for the houses is to really make sure your lens is clearly on and camera out of easy reach (i.e., doesn't look like you're gonna turn it on at any moment). Then, no one bothers you. I think we get a "no photography" reminder just 1 time a visit.
Have fun!
