The best way to explore Cancun is by hopping on one of the public buses that run between the Zona Hotelera and El Centro. The cost is 75¢ no matter how far you go. Taxis from the Zona to El Centro cost anywhere from 150 pesos ($12) to 250 pesos ($20) each way. A more affordable alternative is to catch a north-bound bus to the Kukulcán-Bonampak intersection, which marks the beginning of El Centro. From here, you can explore by foot or flag down a taxi to your area of choice.
A taxi to almost anywhere within El Centro costs around 40 pesos ($3). If you want to get a taste of downtown culture, start at the colorful Mercado Veintiocho or Parque de las Palapas. To return to the Hotel Zone, take a taxi to the Chedraui on Avenida Tulum and then catch a bus that passes every few minutes toward the Hotel Zone