Several trails lead to Oso Pass, including Three Gun Spring Trail, Embudo Trail, Whitewash Route, and Embudito Trail. The hike is pretty strenuous, so take plenty of water and plan on a long day's outing.
The cache is hidden just east of the intersection of Three Gun Spring and Embudito Trail. See http://www.sandiahiking.com for more information about these trails.
Have fun in this beautiful area of the Sandia Mountains. If you are feeling especially energetic, hike another 900 feet in elevation to find Deer Pass Cache, too.