You should definitely go to Markoffs! I have been there 5 years in a row now and have not been disappointed. There are plenty of things to do while you wait too! You can also get a speed pass from two of the restaurants in town, that will allow you to go through the forest as many times as you want and allow you to skip waiting for numbers to be called!
There are also a couple others in the area, but I haven't had a chance to get to them yet.
Field of Screams
Nightmare Manor - Maryland's Best and Scariest Haunted Attraction
And there is one more out at Arundel Mills mall.. but I can't remember what it's called.