Will I have any problem exchanging my dollars or paying with them?
No, whatsoever; you will be able to pay in dollars in the main commercial and service establishments in the City of Oaxaca. This is not the case in rural areas; therefore, it is recommendable to carry Mexican pesos with you on your excursions outside the state capital. The exchange of dollars and euros can be easily done at the bank and exchange offices. Most of them are located in the city's Historic Centre.
Remember that the exchange rate is free and that it may vary a few points from one day to another. Besides, it is not advisable to buy or sell dollars or euros in the black market; although the rates are higher than at the exchange offices, you take the risk of getting counterfeits.

Will my credit cards be accepted?
Yes, their use is quite spread within the commercial and service establishments of the City of Oaxaca. The most accepted credit cards are Visa, Diners, MasterCard and American Express, among others.
Hence do not worry and use them with absolute confidence; however, it is always smart to carry some cash with you, especially for small purchases, to pay for some services (taxis for instance), or if you go away from the urban zone.

Is it advisable to bring traveller's checks?
Yes, because they are a practical, safe and easy way to get cash. These checks can be cashed in at bank offices, travel agencies, some hotels and operators of tourism after presenting an ID, such as your passport, with no inconvenience at all.
It is recommendable to have the checks issued by a known and prestigious financial institution and preferable for large amounts.

How much should I tip?
Although it is not compulsory, it is usual to leave a tip equivalent to 10 or 15 percent of the bill at restaurants, depending on the quality of the service. Luggage haulers, doormen and maidservants are tipped with a dollar.