The best months to go to Mexico beaches are November - May.
July-August, Christmas, and Easter attract huge numbers of holidaymakers from both inside and outside the country, especially at beach resorts. The worst are the hottest and most humid months, June - September, with an insect problem too.
Aug-Nov has the possibility of rough seas on the Pacific coast due to storms.
For diving off Baja California August - November is best, with warm, clear water.
Plus: great varied food and drink are generally available, lively evenings with music and dance are common, coral is superb in some places, some nearby ancient sites are AMAZING [Chichen Itza, Tulum], Spanish is an easy language.
Minus: it's very package touristy in many places, souvenirs are poor, petty theft happens.
Tulum, on the Caribbean coast [picture top left; stormy season just finished so seaweed around!]
One of the prettiest beaches in the world, with picturesque Mayan ruins overlooking the beach.
130 km south of a massive resort of Cancún, it is a tiny but perfectly-formed white sandy cove, with a few palm shade and the azure Caribbean sea to swim in.
The entrance to Tulum is totally touristy, with a huge car park, souvenir shops, café and restaurants. There is no place to stay on the spot, but there are a few hotels and restaurants in Tulum village and also [far better option] plenty of resort type places, cabañas [beach huts] and campsites along the coast road south to Punta Allen.
Playa del Carmen, on the Caribbean coast [not too far from Cancún] [picture top right]
A cool, casual beach scene with plenty of accommodation [though an imbalance towards monster hotels these days], excellent bars, restaurants and shops. Although it is very popular and attracts crowds from all over the world, the place is reasonably low-key, friendly and relaxing.
It is the best place in Mexico to buy high quality crafts, especially jewellery.
It has also boats to Cozumel - for world class diving and a park for swimming with dolphins [at considerable expense!].
Puerto Escondido, on the Pacific coast
Puerto Escondido has several stretches of magnificent sandy beach, with a laid-back ambience and plenty of inexpensive accommodation. Beaches are varied from a 2 km long Zicatela, the surfing mecca [nicknamed the Mexican Pipeline] to the east of the town, to the calmer three coves including Playa Puerto Angelito on the west.
August - November surf reaches 7-8 metre due to south Pacific storms.
Puerto Angel, on the Pacific coast
For even more tranquility go to the Puerto Angel area, including the backpacker's favourite, Zipolite Beach. About 60 km east of Puerto Escondido, there you can find the most simplicity and relaxation [except for the overdeveloped west end] in Mexico.
Recently there has been an increasing security problem. Beware of high surf [particularly August -November] and strong currents in deep water.
Cabo San Lucas and San Jose del Cabo, Baja California [peninsula]
Offering miles of marvellous beaches this is a major American tourist destinations for fishing, golfing or young party animals.
Best beaches are:
Playa Cemeterio 4 km east, Playa Santa Maria 12 km from Cabo San Lucas for swimming, with easy access.
Playa Costa Azul, Playa Canta Mar are ideal for surfing.
Playa Solmar, 1 km west of Cabo San Lucas, is for whale- watching January - April.
Scuba diving and snorkelling are OK, but the the best sites are offshore, reachable only by boat.
Infamous time-share salesmen can be annoying. Beware strong rip tides at some of the beaches.
Bahía Concepción, Baja California
The shore of Bahia Concepcion [Conception Bay], between 10 and 50 km south of Mulegé, has several scenic beaches including Playa Requesón, Playa Buenaventura, and Playa Coyote. The bay is on the coast of Sea of Cortez, which is a protected marine sanctuary. The facilities are fairly basic [some places have no fresh water], but there is wildness, natural beauty, and tranquility. Excellent for watersports and great for seafood, especialy clams. Playa Santispac has the best campsite, with a fine resaurant. If you are up to kayaking, try Playa Buenaventura.
Bahia de Matanchen, San Blas, on the Pacific coast
This small and very Mexican fishing village of San Blas has an excellent town beach, but the best in the area is just 4 km away - Bahia de Matanchen, a broad crescent bay with splendid beaches of prime soft sand and a relaxing atmosphere.
The only drawback is summertime mosquito and sandfly problems.
Between Puerto Vallarta and Acapulco on the Pacific coast
The central Pacific Coast has several hundred miles of coastline with fine sandy beaches and excellent facilities. The choices are enormous from international resorts like Puerto Vallarta and Acapulco for monster all-inclusive resorts packed densely, to smaller resorts with local colour such as: Chamela [the prettiest, 165 km south of Puerto Vallarta], Barra de Navidad and Zihuatanejo. Great activities, fantastic seafood, and lively night life.