There's quite a number of mobile internet providers with Telcel, Movistar, and Lusacell being the major internet service providers.
Personally, I recommend Telcel as it has a wider coverage compared to the other internet service providers and in case of any issue, they have several customer service offices all across the country where you can get assisted.
If you are landing at Mexico city's Benita Juàrez international airport there's quite a number of authorized dealers who can set up your Telcel SIM card for you.
For prepaid internet
1.5 GB valid for 15 days is 249 pesos
3 GB valid for 30 days is 399 pesos.
You can also build your own internet plan based on your budget.
NOTE: Prepaid minutes are also available
For more info and inquiries regarding Telcel mobile services visit their website