For added functionality you will likely want your phone to do a couple of the things it normally relies upon data for that will make your stay a lot less stressful and may facilitate understanding
- an offline maps app
- an offline ENG/ESP dictionary
It's an eerie feeling when you reflexively open your maps app only to find, at most, a lovely view of wherever your flight to Cuba left from. At worst the app doesn't even open. There are a few options in offline maps that we'll cover here and of course a simple web search will provide many more. These are free and functional but if you want added functionality - like GPS navigation - that might cost you.
Google Maps brought back (ok, it never left but they stopped hiding it) a feature with its 3.0 update that allows users to save area maps offline. You'll need to zoom over the area you're planning on traveling to then tap in the search bar. Depending on whether you're using Android or iOS you'll see some language akin to 'make map available offline'. Tap, accept, download, you're set.
Another, more holistic solution is MAPS.ME. This is a freemium service that allows you to download whole geographic areas (like the island of Cuba) in one hulking swoop (like 50mb) for your use later. This app shows your area in great detail and has features that allow you to drop and save personalized pins but navigation is a paid feature.
My personal favorite is OsmAnd which has detailed maps and offline navigation. This open source solution does a lot - maps, routing and navigation - and does it well.