My mother in law has not seen my son since he was a baby , what visa do we file so she can come and visit for awhile ?

Your mother-in-law would typically apply for a B-2 visitor visa at the American consulate or embassy with jurisdiction over her place of residence. In doing so, she would have to show ties and bonds with Mexico to demonstrate that she would return to Mexico after the time of visit. If she is lacking funds, you and your spouse can guarantee her support during the time that she is here with an affidavit of support along with materials such as your job letters, banking statements, and most recent tax return. Please note that the issuance of a visitor visa is within the discretion of the US consular officer. Good luck!  Due to the limitations of the Lawyers.com Forums, Alan Lee & Arthur Lee, Esqs.’ (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.