In general, reserve a car in advance from home to get the best weekly rates during high season (Nov-Feb); in low season, renting a car after you reach Mérida often yields better deals from local rental companies that offer promotional deals that you can get only if you are there. Always ask if the price quote includes the IVA tax and insurance coverage. Practically everybody offers free mileage. If your visit will be primarily in Mérida except for a couple of day trips, you'll do better to rent for just a day or two, which also spares you the high cost of Mérida's parking lots. These estacionamentos often charge one price for the night and double that if you leave your car for the following day. Many hotels offer free parking, but make sure that includes daytime hours.
Taxis are easy to come by and much cheaper than in Cancún, usually 30 to 60 pesos around town and 100 to 120 to the outskirts.
City buses are a little tricky to figure out but aren't needed often because almost everything of interest is within walking distance of the main plaza. The most useful buses run between downtown and Paseo de Montejo, which is a bit of a hike from the plaza. Catch an "Itzimná" bus on Calle 59, between calles 56 and 58, to visit points along the boulevard. You can also take a colectivo (minibus) heading north on Calle 60. Most take you within a couple of blocks of Paseo de Montejo. The colectivos or combis (usually painted white) line up along the side streets next to the plaza and fan out in several directions along simple routes.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.