Yes, the US is one of only two governments that taxes the worldwide income of its citizens who reside overseas. So you must file US taxes each year, no matter the country in which you reside. Also, you may also be required to file an informational return – called Foreign Bank Account Reporting (FBAR) – on your assets held in foreign bank accounts
Thankfully, the US has a special arrangement which protects you from double taxes in Mexico. With proper planning you can take advantage of the rules to minimize, possibily elimiate your US taxes.
FYI, even if you don’t owe any taxes in the US, you are normally still required to file a return.
Bottomline, get an expert to help with your tax arrangements. The savings should more than cover the cost.