Here's what Rough Guide says: Cash US dollars and 'convertible pesos' (equal to US greenbacks in Cuba; worth the same as Monopoly money elsewhere) remain the currency of choice at state-owned and licensed private hotels and restaurants; bus, train and airline offices; and most other tourist-oriented enterprises. Cuban pesos, or moneda nacional, can be used at local venta libre stores, cafeterias and street stands, cinemas, and many other businesses away from popular tourist destinations. Candeca, with kiosks throughout Cuba, changes currency at fair rates.

http://www.lonelyplanet.com/destinations/caribbean/cuba/money.htm

You are not allowed to take much Cuban pesos or moneda nacional out of the country so get rid of them there. The convertible pesos aren't worth anything outside of the country.

You may not need the tourist pesos if you are travelling independently.

Frances Toronto, Canada