Flying still represents good value for money in Mexico, especially considering the long, hot bus trip that may be the only alternative. In recent years, the large airlines have left many of the domestic routes to smaller carriers. However, these start-up airlines and their timetables are particularly volatile; new ones are founded and older ones flounder at an alarming rate. The majority of domestic air connections go through Mexico City.
Buses are the most common mode of public transport and bus routes are extensive. Long-distance buses are fairly comfortable, air-conditioned (bring a jumper!) and acceptably fast. Local rural buses tend to be ancient, decaying, suspensionless models grinding out their dying years on dirt tracks. Combis, colectivos and peseros are minibuses used for local transport. Note that highway robbery is a real risk in Mexico, especially at night on isolated stretches of highway.
Driving in Mexico is certainly not for everyone: you should know some Spanish, have basic mechanical aptitude, large reserves of patience and access to cash for emergencies. However, it can be just about the only way to get to some of the most beautiful and isolated towns and villages, although you need to be forgiving of road conditions.
Car and passenger ferries connect Baja California with the Mexican mainland; ferries also run between the mainland and the Caribbean islands of Isla Mujeres and Cozumel. Thanks to the government's privatization of Mexico's railways, most of the country now lacks a passenger train service. The exceptions are special tourist-oriented lines such as the Copper Canyon line from Chihuahua to Los Mochis and the Tequila Express from Guadalajara to Tequila.