Take the Speedway exit from the I10. This exit is also marked as the University of Arizona
Drive east along Speedway for about 2 miles. One of the many stop lights is at Cherry Ave. Turn right (south) along Cherry, and start looking for parking. The address of NRAO 949 N. Cherry Avenue. This is the Steward Observatory building, and NRAO occupies the 5th (top) floor of that building. There is a 30-minute loading only parking spot on the west side of the road, immediately outside the Steward Observatory building. Otherwise, go to the parking garage on 2nd street, going west from Cherry Ave.
The first map below takes you from the I 10 Speedway intersection, about halfway towards NRAO. The map below that overlaps slightly, and completes the trip to NRAO. NRAO is marked by a small rectangle. The building is northwest of the Flandrau Planetarium, on the opposite side of Cherry Ave.