Customs

When you arrive in Cancun you will have to go through customs. Since November is not high tourist season, this process should not take to long. Also to enter Mexico you will need at least a birth certificate and an ID (current, valid photo identification), but getting back into the U.S. with only those documents is a bit more of a hassle. Getting a passport is recommended for hassle-free re-entry. Passports only simplify the process and nobody wants to be held up or questioned while going thru customs. For additional information on passports check out the following website:
http://travel.state.gov/travel/tips/regional/regional_1174.html