Firstfield Rd @ Quince Orchard Rd is a busy intersection. Ride On route 56 southbound and route 61 westbound both turn right at this intersection. Like many intersections in the county, there is only one crosswalk to cross Quince Orchard Rd, which means you may have to cross the street three times to reach the bus stop.
Cache is not at posted coordinates. You should get off the bus at posted coordinates. Last three digits of longitude and latitude of the final location are given in the picture below. Visiting Smithsonian's The Great Inka Road: Engineering an Empire may help you understand the puzzle.