Any contract that you sign in Mexico, whether for real estate or anything else, will almost always be in Spanish. It is possible that you may draft a contract with another person in English but if there is ever a dispute, it will be translated into Spanish for the judge to read. For that reason, it is important to get an official translation of any legal document that you sign. It also is a great idea to get an attorney who is fluent in both English and Spanish. He will be able to analyze the document in Spanish and then to explain it and answer any of your questions in English.
If by chance you do have a document in English, it is still a great idea to get a good translation. Then you have something for your own reference. Again, it is best to get a good bi-lingual attorney to go through both documents with you. It is wise to consider that even an official translation may have subtle differences in legal interpretation so it is always wise to have your attorney carefully review the Spanish document.
There is one exception to the statement that all official documents are in Spanish. The government recognizes all indigenous languages and must provide official documents in those languages if requested. There is a possibility of a document being controlled by the indigenous language.
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