Why do some rivers in Mexico have rio front of it and others river?

The use of "río" versus "river" in the names of rivers in Mexico depends on the preference of the people there and historical factors, rather than any linguistic or geographic rules. Both terms are used interchangeably and can be found in different parts of the country.

In general, the term "río" is more commonly used in Mexico to refer to rivers, as it is the Spanish word for river. However, there are some exceptions where the English word "river" is used, particularly in areas with a strong English influence or historical connection.

For example, the Rio Grande, which forms part of the border between Mexico and the United States, is commonly referred to as the "Río Bravo" in Mexico. On the other hand, there are also instances where the English word "river" is used, such as the Colorado River (Río Colorado) in northwestern Mexico.

In summary, the use of "río" and "river" in the names of rivers in Mexico is based on local preferences, historical conventions, and the influence of different cultures and languages in different regions.