Wi-fi is virtually nonexistent on the island, though you can usually find it at the Casa de la Cultura near Conaf's administrative headquarters. Those who need to stay connected (and have an unlocked phone) should consider purchasing a Movistar SIM card on the mainland.
There are no banks or money changers on Isla Robinson Crusoe, so bring all the pesos you'll need, preferably in small bills. Some businesses will take US dollars or euros, albeit at poor rates. Credit cards are rarely accepted outside of the higher-end guesthouses.
Experience Robinson Crusoe (www.experiencerobinson.com) is a fantastic English-language resource for the latest island information.