Currency management in Argentina can be a bit of an adventure. You'll find that you need to use cash here much more than at home, and often very small (and old!) bills and coins. Be informed, and you will be well on your way.
The only currency used in Mendoza is Argentine Pesos. But don't fret, local currency is easily withdrawn from an ATM machine.
HSBC and Banco de Nacion are the most common banks in Mendoza, and are a good first stop for withdrawals. Keep in mind you will be charged an extra fee for withdrawals. As with any international trip, be sure to notify your bank you will be using the card in another country before leaving.
Many restaurants, wineries, and stores in Mendoza do not accept credit cards. Also, note that very few establishments allow you to tip on your credit card even if you are able to pay with it. Be sure to have your Passport # with you for making all credit card purchases, but leave the original locked up in the hotel.
There is a shortage of small bills and change in Argentina, especially coins. Most merchants won't be able to break your larger bills. The easiest way around this is taking out $290 instead of $300 when you visit the ATM. Save your big bills for restaurants and chain stores, or ask about change before making your purchase.
In restaurants, it's customary to tip about 10% of the bill. Even a small tip (propina) will be appreciated. Taxi drivers don't expect tips, but it's customary to round up to the nearest peso.
Location of major banks in Mendoza include: