Cancún runs on dollar prices in the Hotel Zone and peso prices two bus stops away. Every beach on the island is legally public and free, downtown feeds you for under MX$100 a day, and the R1 bus links it all for MX$12 a ride.
Blvd. Kukulcán km 2.5, the Hotel Zone's smallest public beach and the only one on the calm bay side. Free showers, palapas and a playground; the water stays waist-deep for 30m. Open 24h, lifeguard 09:00-17:00.
Av. Kabah at Av. Nichupté: 41 hectares of protected mangrove and dry jungle inside the city. Free entry 06:00-19:00, 3km of paved trails, and resident coatis, iguanas and spider monkeys along the boardwalk.
Km 6.5, a free public beach with a wide sandbar, a municipal dock and the cheapest food on the island — ceviche tostadas around MX$60 at the palapa stands. Toilets cost MX$10, the beach itself nothing.
A 2km lagoon-side boardwalk between Av. Bonampak and the Nichupté mangroves, free and open at all hours. Crocodiles surface near the wooden viewing decks at dusk and the sunset hits the lagoon straight on.
Calle Cedro off Av. Tulum: the market locals actually use, a third the size and half the price of Mercado 28. Open 07:00-17:00 for herbs, piñatas and copal; the fondas at the back serve a three-course comida for MX$80.
Downtown's main square, ringed by about 30 food stalls under thatched roofs. Marquesitas MX$35, panuchos MX$15, esquites MX$30. Free live music and clown shows take the bandstand most evenings from around 19:00.
Av. Tulum 17, Cancún's oldest craft market, trading since 1975. Free to wander the 100-plus stalls of hammocks, guayaberas and obsidian; haggling realistically starts at half the asking price. Open 09:00-21:00.
The downtown strip where cancunenses eat: taquerías, marisquerías and cantinas along six blocks between Av. Uxmal and Av. Cobá. Tacos al pastor run MX$18-25 and a michelada about MX$60, with no cover anywhere.
Km 5, a small free beach on the sheltered bay with a public pier reaching 80m into the water. Shallow, wave-free and busiest with local families on Sundays; the showers and shade palapas cost nothing.
Km 12.5, a 13th-century Mayan lookout temple standing on the dune between the Park Royal and Westin hotels. No ticket booth and no fee — reach it from the public beach access beside Plaza Kukulcán, daylight hours.
Km 24 at the island's southern tip, a rocky cove where the reef begins about 40m offshore. Free entry down a steep sand path; bring your own mask as there is no rental. Calm before 13:00, choppy afterwards.
A free public boardwalk circling the Puerto Cancún marina, open until 23:00. Benches face west over the yacht basin for sunset, and the supermarket inside sells beer at MX$25 against MX$120 at the beach clubs.