Where are you going in Mexico ?
If Cabo area, USD are common currency for spending and tipping.
However, for other parts of Mexico PLEASE use pesos ! If a worker receives USD they have to spend time standing in line at a bank for the best exchange rate converting USD to their country's currency of pesos.
Tipping guidelines: 20p for each drink for each person (that's about $1 USD), 50p (about $2.50 USD) each day to housekeeping, don't wait until the end of your trip to tip as housekeepers can change daily.
Enjoy México 🇲🇽