Bulldog is a trail that must be reached by other singletracks. At the trail head is a map with great info. Bulldog is a great crosscountry ride with a great up hill and amazing downhill.
Take Bullion rd (aka croy canyon) west out of the center of Hailey. Continue past the animal shelter. Turn right about 3 miles out onto Trail Head rd. Get after it!
http://www.singletracks.com/item.php?c=1&i=4187