The majority of the swimming is done at pools located at the resorts. If you venture into the water along the shore, be prepared for large waves and rip-tides. It is not uncommon for there to be no lifeguards at the beach. The eco-parks tend to have better areas for one to swim, unless you prefer a pool. They are located in sheltered bays, with clear, clean water.
One should take care when driving, you will be sharing the road with cars, trucks, cattle and people. Take care and use caution and you should be fine. Driving after dark is a bad idea. Too many ways to have problems! The Policia are friendly, treat them with respect. Plan on being stopped at state borders and your vehicle may be searched. Just go along with it. The Federal Police, patrol the area and they are a serious bunch. Be polite with them and do not photograph them, any military vehicles or establishments.
Due to problems in the past, spring breakers are not the favorite visitors with law enforcement. Don't push their buttons. Behave like an adult and you will have few problems. Behave like a drunken fool, and you may regret it, for a long time. Same goes for most places.
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The official language is Spanish, like in the rest of the country. In the tourist areas, many locals also speak English, and some others French, German and Italian, as this area receives tourism from those places. However, some locals trace their heritage to the Mayans who settled the area before the arrival of the Spanish. The present-day Mayans tend to live inland and speak little Spanish.