Please make a checklist and make sure you carry all documents without missing, so your visa process will be smooth.
Recommended Document
Get Mexican visa at near by Mexican Embassy for being on safe side & to make your travel smooth with out any issues. It will be valid for 6 months and you can travel to any city in Mexico.
NOTE: Activate International Travel Plan If you want to use AT&T in Mexico, AT&T has coverage in Mexico as well. While in US itself, talk to AT&T & get this plan activated. Costs 10$/day. T-Mobile works in Mexico as well. Other carriers, please talk to customer care once.
Carry Cash as listed below:
30$ for Temporary Mexican Visa @ Border.
6$ for I-94 at US Border while coming back to USA.
2$ worth of quarters.
Cash for paying us in matamoros Mexico depending on your situation(single/family/with friends)
Credit card that can allow foreign transactions for purchasing at stores, food @ subway, restaurants, movie theaters, malls etc.,
Note : Try to take credit card that does not charge any international fee(Like travel credit cards), Also intimate your credit card company about your travel, so they will keep your card open for your transactions without blocking
Mexico currency is Pesos, there will be foreign exchange centers which can help you to exchange dollars into pesos if you need.