There are many transfer providers in Mexico that offer international money transfer services and often offer cheaper transfers than the banks. Using one of these providers makes sense especially if you want to transfer larger sums.
For smaller amounts an alternative way of transferring money to Mexico is to simply use a foreign bank account and withdraw funds from this account at a Mexican ATM. You will be charged a fee for each cash withdrawal, check at the bank for the exact percentage.
Money transfer agencies in Mexico
If you need to quickly transfer cash from abroad to Mexico (or vice versa), one of the fastest ways to do so is through an international money transfer agency like Western Union. The person sending you money deposits the cash at an agency office in their country and explains where the money should be transferred to. Immediately afterwards you can go to an agency in your destination and pick up the money with a proof of identity. Unfortunately money transfer agencies also charge hefty fees on these transfers, so this will not be a cost-effective option on large or regular money transfers.
Internet services for transferring money to Mexico
You can also use one of the large online payment services like PayPal or Money Bookers for transferring money to Mexico. Fees and procedures vary so shop around before deciding on one.