I'm heading to Cuba in February and wanted to know if I should bring my aluminium road bike or my mtb? Also any tips.
I took a gravel bike and my wife a road bike (Synapse) - you certainly don't need a mountain bike.
It can be a challenging destination if you're using to European or American cycling holidays. Lots of interest if you can put up with regular hassle and inconvenience, and the difficulty of finding decent food. Those picturesque old cars are also the most foully polluting vehicles I've ever encountered.
To expand a bit on Jez's post, the bike depends on where you go. When we were there 2 years ago parts of the "road" from Pilon to Uvero had washed into the sea and some of the bridges although rideable had collapsed. Some roads in the hinterland (e.g. Topes de Collantes) unexpectedly turned from paved to gravel and back.
It is a poor country where tourism is important to the economy - expect all the attendant good and bad experiences. Depending where you are, food in the shops (and bottled water) can be difficult to very difficult to find. You will always eat well in the Casas Particulares. The state run hotels outside the tourist areas are not worth staying in except in an emergency. Outside the main tourist areas you will probably need to speak some Spanish. It can be very windy and most people just cycle west!
The public wifi system works reasonably well once you get the hang of it. Withdrawing money from ATMs was relatively painless and a much better option than queuing in the bank.
Wally and Barbara's book was accurate but a bit out of date. The Lonely Planet guide was inaccurate (e.g. bus station in the wrong location in Santiago). Maps are generally speaking not available and road signs sporadic, but we didn't get lost.