There are two parts of Cancun generally frequented by visitors: the ‘hotel zone’, and central Cancun, which sort of starts at the rotary where Blvd. Kukulcan meets Av Coba. The best running options in central Cancun are below. Many are overlapping and can be combined.
Bike Path. This starts at ‘km zero’ near the rotary and is a red-colored path that stretches for ~10 km toward the hotel zone. The first 5 km extending from the center are the nicest. Bonus: lit at night!
Malecón Tajamar. A nice little section of road with good water views. It’s ~1.5 km from the main rotary in Cancún/km zero of the bike path. Pleasant, palm-lined road with good sidewalk. The nicest stretch is the 1 km or so along the water, along Avenida Malecón Fonatur, a delightful walkway along the Nichupte Lagoon with great views. Overall, a 5 km loop from the rotary. MAP
Kabah Park. Enjoy ~2.5 km of running paths, nicely shaded and featuring lovely tropical foliage. It’s about 1.5 km from the Malecón area/Highway 30.7. Can be combined with Malecón Tajamar, for a longer run.
Av. Tulum. Cancun’s ‘main street’ has been improved lately, with a wide pedestrian path and landscaping. It’s about 4 km from the Dubai Palace Casino north to El Crucero Park. Pass shops, restaurants, City Hall, Plaza de la Reforma.
Roads Around the Port. If you’re looking for some quieter roads near the center, some of the streets around the port are good for running. One can put together 2-3 miles combining Puerto Cancún Rd. and some of the spur roads off it, such as Puerto Escondido. Some sections are a bit industrial, with the perpetual construction that characterizes Cancún, while other sections have some nice marina/harbor views. The beach in this section is narrower and rockier.
Ave. Huayacan Bike Path. For variety and to get off road, the bike path that runs along Ave Huayacan. towaed to airport is a good option. About 15 km, most of it on dedicated path. Not beautiful, but a good, safe, straight shot for those who want to get in the miles.