Forget those art wimps and New Age loonies--beach bums have been coming to Todos to surf and camp long before you could get an espresso or Shiatsu massage there.
There are beaches walkable to from town (a couple of desert miles, though) but they are not the best for swimming due to extremely violent waves and undertows. Pretty and isolated places though, like La Posa (walk up Calle Topete until it turns into a path leading towards the sea) or Punta Lobos head out of town on Degollado past the old fish plant. This is a great sunning and partying beach, and there are often sea lions about. In the afternoon fishing skiffs put in and you can buy your dinner cheaper and fresher than at the markets or restaurants.
The more useful beaches are accessible off the highway. Swimming is best at Las Palmas and Los Cerritos, about 8 miles south on the highway, just past Gypsy's Bed and Breakfast. Las Palmas is a serene beach lined with (duh) palm trees for a look almost like the mainland (or Hawaii) not typical of Baja at all.
Los Cerritos is a pretty beach with good fishing, an RV pask ($4 US a night)and a nice right break for surfers.
Further south, at about Km 81 is a Plays Las Cabrillas, not so good for surfing but popular with campers. This is your best bet to find a bunch of rasta-locked kids doing a drum circle and running around bareass. Nearby Playa San Pedrito is the same way, skinny-dipping (not a very good idea in Mexico, by the way) and camping.
Further south, at Km 97 is a marked dirt road to Estero Migrino. This estuary has birds and wildlife and during the winter pumpos out a nice right break.
None of these places has water, so bring your own. In Todos Santos, by the way and like many towns in the Baja, the water comes from deep wells and is potable right out of the tap.