don't have any tips..
but i can tell you this.
DO NOT USE DOLLARS!
You'll lose out on the conversion.
The current exchange rate is around 17.50%
So for every $1 USD = $17.50 Pesos ($100 USD = $1750 Pesos)
when i first came to Mexico.
i was using Dollars in place of Pesos..
Mexicans loved me..
until i discovered why.
FYI: Mexicans know this and will be more than happy to take your Dollars