Taxis and walking are the best choices. Buses are common but hard to use. The subway is good, but has limited coverage.
Taxis
Taxis are the easiest way to get around Monterrey. The green and white Eco-Taxis are most common, and they are both affordable and plentiful. Taxis use meters in Monterrey, and to avoid overcharges, insist that the driver use the meter. The average fare for an in-city trip will be about 50 pesos. The fare from downtown to the airport will be about 200 pesos.
Car
Renting a car is a possibility, though it can be expensive and navigating the streets can be a bit tricky. As with any major metro area, parking is always an issue, though parking is generally easier in Monterrey than in other cities of similar size. Many downtown hotels offer free parking and free valet parking for their guests. A large public lot under the Macroplaza usually has spaces available.
By bus
The buses in Monterrey go through the city numbers 1-199 go in a certain part of the city.Numbers 200-300 go to most part of the city.And 300-502 are minibuses. Also there is a metrobus service in Guadalupe and San Bernabe area.Theres three routes in San Bernabe and one in Guadalupe. For more info go to Metrorrey website..
Downtown Tourism Transportation
In the downtown area, there is a tourist trolley that does regular circuits around the Macroplaza and Barrio Antiguo areas.
Riverboats on the Paseo Santa Lucia can be used to go between the Macroplaza area and Parque Fundidora. The boats leave from the waterway below the Museo de Historia Mexicana, near the Palacio del Gobierno.
Subway
The Metrorrey subway system is clean, modern, and very inexpensive, though the coverage is not extensive. It can be used to go between downtown areas like Macroplaza or Barrio Antiguo and the Central de Autobuses bus station. It also stops near the Cerveceria Cuahtemoc and the Coliseo and is a good choice if you are staying in the suburban municipality of Guadalupe. The useful stops for a tourist include:
Central: main bus station, Coliseo
Cuahtemoc: transfer point, low-end shopping, brewery tours
Padre Mier: shopping near Morelos Zona Rosa, Holiday Inn Centro
Zaragoza: Macroplaza, Barrio Antiguo, Howard Johnson, Fiesta Americana, Santa Rosa Suites
Parque Fundidora: Parque Fundidora, Cintermex, Arena Monterrey, Holiday Inn Fundidora
Universidad: Universidad Autonoma de Nuevo León, Parque Niños Héroes, Estadio Universitario