You can camp on the beach for free north of the ferry terminal at Playas Pichilingue, Balandra, El Tecolote, and El Coyote. Among these options, only El Tecolote has freshwater; plan to bring all your supplies from La Paz [1]. Two restaurants at El Tecolote sell food and drinks. Though not common, theft unfortunately does occur at these beaches. Keep valuables out of sight if at all possible.
Only a couple of RV campgrounds remain as real estate development continues in the greater La Paz area. Oasis RV Park (Km. 15, El Centenario, tel. 612/124-6090 or 612/125-6202, open year-round, US$14) is one of the survivors. It has a good location on the Ensenada de La Paz; however, its 25 sites are best reserved for self-contained rigs, as services have been limited in recent years. Tents are welcome, too.
Much closer to town and with much better facilities, popular Casa Blanca RV Park (Km. 4.5 at Pez Vela, Fracc. Fidepaz, tel. 612/124-1746, rv.casablanca [at] gmail [dot] com, Nov.–May) has more than 40 full-hookup sites for US$20 per night or US$400 per month. The property is surrounded by a high white concrete wall and the park provides 24/7 security. Inside, facilities include hot showers, flush toilets, laundry, and a small convenience store—but there is no dump station. Guests may use the swimming pool, tennis court, and spa. The park does not have Internet, but there is an Internet café open to the public just a short walk away.
You can also camp on the Isla Espíritu Santo, which is protected by the Mexican government. Permits cost US$4/day. Visit the local SEMARNAT office (2nd floor, Ocampo 1045, btw Rubio/Verdad, tel. 612/128-4171, www.semarnat.gob.mx [2], 8 A.M.–3 P.M. Mon.–Fri.) before you head out to sea. Pets are prohibited, as is harvesting wood for campfires. The availability of freshwater limits camping options on the larger islands, and camping is not allowed on Ensenada Grande or Playa Ballena.
Two of the bays, Caleta El Candelero on Isla Espíritu Santo and El Cardonalcito on Isla Partida, have freshwater wells where you can bathe. You’ll need a bucket and five meters of rope to reach the water level. Purify the water if you must use it for drinking. (Plan to bring your own purified water and only use the well water in an emergency.) It’s also a good idea to bring multi-fuel stoves for camping to increase your chances of finding the canisters you need while in Baja.
Links:
[1] http://www.moon.com/destinations/baja-cabo/cabo/la-paz
[2] http://www.semarnat.gob.mx