You can get to Playa Madera from San Juan del Sur by water taxi, taxi, or bicycle. The water taxi can leaves from Hotel Estrella at 10am and returns at 4pm, and costs about $8. A taxi cab for two people costs about $10-$15; the road is rough, and you may have to get out and walk up a hill or two while your cab driver tries to drive up backwards to take advantage of the front-wheel drive. A bike can be rented in San Juan del Sur for about $5 per day.
Walk.
A nice beach, some good surfing, and good walking along the beach to the north.
Surf, rent a surf or boogie board (about $10 a day), or get a lesson (also about $10). You can take a short walk north to another nice, more secluded beach offers less threatening waves for surfing or boogie boarding.
There is a food stand that sells basic food/snack items. There are no ATMs or banks, and the food stand does not accept credit cards.
Water and beer can be purchased from the food stand.
Some rooms may be available at the surf camp, and you may also be able to rent a hammock (with limited privacy and potentially no secure place to store your bags).
North of Playa Madera is another small beach, home to a basic hostel called "The Hideout" that serves dinner for about $5 per person, as well as Matilda's, a family-run place with shared dorms, two-person rooms, little "dog house" huts and some fancier rooms as well, with prices ranging from $5 to $25 per night.