As I know there is NO public transportation in Nogales. So, you must have or rent a car to get around or you can walk around Nogales downtown as well.
The traffic was light in this sleepy bordertown at least when I was there as you can see on my picture.
Nogales is a border town, located in southern Arizona on a border between Mexico and the USA. There are two cities seperated by the border line: USA Nogales and Mexican Nogales.
I drove there I-19 (Interstate freeway 19) from Tucson. It took me more than 1 hour (70 miles = 110 km). As I was looking for accommodation I took exit 8 to I-19 BUS (business) and after a few miles I noticed tall lighted commercial of Motel 6 on right. Hmm... I could continue driving I-19 to exit 4 to get to Motel 8 (or Super 8 Motel at West Mariposa Road earlier this way).