Is it safe to drink the tap water?

No. Always drink bottled or filtered water.

Should I learn Spanish?

You don't need to be fluent, but knowing basic phrases makes navigating buses and markets much easier.

Is it better to take the bus or fly between cities?

Buses are better for seeing the landscape and saving money; flights are best if you only have 14 days and want to minimize transit time.

Planning a 2-Week Mexico Backpacking Route

Focus your route on a single region rather than trying to see the entire country. Stick to the southern circuit of Mexico City, Oaxaca, and the coast of Oaxaca for the best mix of culture, food, and beaches without spending your whole trip in transit.

Choose your start and end hubs. Fly into Mexico City (MEX) and out of Huatulco (HUX) or Puerto Escondido (PXM). This saves you a 12-hour bus ride back to the capital at the end of your trip.
Use ADO buses for long hauls. Book your inter-city travel via the ADO bus line website. Their 'GL' or 'Platino' classes are worth the extra $10 for reclining seats and legroom on overnight routes.
Limit your stops to three main locations. To keep travel stress low, spend 5 days in Mexico City, 5 days in Oaxaca City, and 4 days on the Oaxacan Coast.
Use domestic flights for time-sensitive legs. If you are short on time, a 1-hour flight from Oaxaca City to Puerto Escondido costs about $60–$90 and saves you a brutal 7-hour mountain road trip.

Is it safe to drink the tap water?: No. Always drink bottled or filtered water.
Should I learn Spanish?: You don't need to be fluent, but knowing basic phrases makes navigating buses and markets much easier.
Is it better to take the bus or fly between cities?: Buses are better for seeing the landscape and saving money; flights are best if you only have 14 days and want to minimize transit time.