Your passport (or birth or naturalization certificate) is your positive proof of national identity. Don’t leave home without one. U.S. Immigration rules require that all U.S. citizens must have a valid passport in order to re-enter the United States.
For U.S. and Canadian citizens, entry by air into Mexico for a few weeks could hardly be easier. Airline attendants hand out tourist cards (tarjetas turísticas) and officers make them official by stamping them at the immigration gate. Business travel permits for 30 days or fewer are handled by the same simple procedures.
A good physician can recommend the proper preventatives for your Oaxaca trip. If you are going to stay pretty much in town, your doctor will probably suggest little more than updating your basic typhoid, diphtheria-tetanus, hepatitis, and polio shots.
For remote tropical areas—below 4,000 feet (1,200 meters)—doctors often recommend a gamma-globulin shot against hepatitis A and a schedule of chloroquine pills against malaria. Use other measures to discourage mosquitoes and other tropical pests. Common precautions include mosquito netting and rubbing on plenty of pure DEET (N,N dimethyl-meta-toluamide) “jungle juice,” mixed in equal parts with rubbing (70 percent isopropyl) alcohol.
The majority of visitors reach Oaxaca by air, and a large fraction of those through Mexico City. There, travelers transfer to flights bound for either Oaxaca City , Puerto Escondido , or Bahías de Huatulco  and Puerto Ángel .
But bus travel rules in Mexico. Hundreds of sleek luxury- and first-class bus lines roar out daily from the border, headed south. The route to Oaxaca along the Pacific shore, although the longest, requiring one or two transfers and at least three full 24-hour days, is the most scenic. Within Oaxaca, a host of lines connect virtually every town and most villages. Three distinct levels of service— luxury or super-first class, first class, and second class—are generally available.
If you’re adventurous, but still want to have all the comforts of home, you may enjoy driving your car or RV to Oaxaca. On the other hand, consideration of cost, risk, wear on both you and your vehicle, and the congestion hassles in towns may change your mind. Oaxaca car rentals are not cheap. With a 15 percent or more “value added” tax tacked on and mandatory Mexican car insurance , they run more than in the United States.