Electricity in Acapulco is the same as it is in the U.S. and Canada, 110 V / 60 Hz. This is a good thing because you won't fry your equipment.
Wall sockets, however, do not always accept US plugs. Mexico uses three types: the three prong socket that we are all familiar with, the two prong socket that receives a fat ended plug prong, and the two prong socket that will not accept the fat-ended plug prongs. It is this last type that can cause problems. You may need to go looking for an adapter (in Spanish, adaptador (ah-dahp-tah-DOHR).
Though hard to distinguish in the photo, both prongs on this adapter are the same. It is the most common type of plug in Mexico and is highly recommended, especially if you plan to stay in the older section of town.
Below is the culprit, the plugs that have one fat prong.
The orange adapters used to fix the problem cost less than $1.00 USD and are available at Wal-Mart as well as local hardware stores. (There are two Wal-Marts: in Costa Azul and in Acapulco Diamante).