For detailed information on all of Mexico's passport and visa requirements, consult the website of Mexico's INM (National Immigration Institute): www.inm.gob.mx. Be aware that visa and passport regulations sometimes change, so check with your nearest Mexican embassy or consulate ahead of time.
If you are a citizen of any of the following countries then you do not need a tourist visa to enter Mexico: Andorra, Argentina, Australia, Austria, Belgium, Canada, Chile, Costa Rica, the Czech Republic, Denmark, Finland, France, Germany, Great Britain, Greece, Hungary, Ireland, Island, Israel, Italy, Japan, Liechtenstein, Luxembourg, Monaco, Netherlands, New Zealand, Norway, Poland, Portugal, Puerto Rico, San Marino, Singapore, Slovenia, Spain, South Korea, Sweden, Switzerland, United States of America, Uruguay or Venezuela. However, you will need a valid passport and to fill out an immigration form for tourists and business trips. These can be obtained in travel agencies, airlines or at the point of entry.
If you are a citizen of any other country, please go to your nearest Mexican consulate to request a tourist visa.
If you are looking to come to Mexico to live and work, the process can be a bit tricky. You need to get authorization - in the form of a work visa - to do so from the INM and demonstrate that you have an employment offer from a Mexican business. To study in Mexico, you will need to apply for a student visa from the INM. To do so, you will need to show proof of enrollment in a Mexican school as well as sufficient funds for the duration of your stay.
Note: Keep in mind that visa procedures can take several weeks and you may have to apply for it from within your country of residence or citizenship.
Every tourist entering Mexico has to get the Mexican Tourist Card (FMT), a card document that must be filled out and stamped upon entry and kept until you leave. These cards are available at a host of places: official border crossings, international airports, travel agencies, Mexican consulates, airlines, etc. The card details the length of stay, which is filled out by immigration officers. The maximum stay is 180 days for most nationalities, though for some countries the maximum is 90 days. Unless you tell them specifically how much time you need, officers will often put a number much lower than the maximum. In case you end up delayed or with changed plans, it's always adviseable to give yourself some extra time.
This card permits you to engage in what are deemed "touristic" activities. If the purpose of your travels to Mexico is to work, volunteer, report, study, etc., you may need a visa. Check with your nearest Mexican embassy or consulate.
The Mexican Tourist Card itself is technically free of charge, but carries with it an obligatory tourist fee (DNI, or nonimmigrant fee) of about $20. If you enter Mexico by air, the fee is included in your air fare. If you enter by land, you must make the payment at a Mexican bank or border post anytime before you re-enter the frontier zone or, if you're flying out, before you check in at the airport.
Make sure to hold on to your card for the duration of your stay. Should you lose it, acquiring a replacement - for which you have to contact your nearest tourist office, embassy or consulate for an official authorization to take to the INM - will put a $42 dent in your wallet.
The number of days on your card can, should your plans change, be extended up to the maximum number of days permitted (180 for most countries, 90 for some). The INM has offices in many cities and towns that can administer extensions; the process generally takes just a couple of hours and will cost around $20. You will need a variety of documents, such as your passport and tourist card (originals and photocopies) and at times proof of sufficient funds.
Should you lose your passport, need a visa or find yourself in some sort of legal predicament, your first stop should be your country's nearest embassy, consulate or consular agency. Passport replacement and visa issuance procedures can take anywhere from a couple days up to over a week, depending on your nationality and embassy. Keep in mind that embassies, consulates and consular agencies generally operate between the hours of 9am and 2 or 3pm and close on Mexican as well as their specific national holidays.
The majority of foreign embassies in Mexico are located in Mexico City, which is easily accessible through Guanajuato's bus station or airport. However, most countries additionally have consulates and consular agencies taht can handle embassy responsibilities and services; these branches are dispersed throughout Mexico's regions and therefore may be nearer and more convenient.
For full listings and contact information of all foreign embassies, consulates and consular agencies in Mexico, you can consult the national Ministry of Foreign Affairs official website: www.sre.gob.mx (in Spanish & English).