It is great because you will really get to know the city and experience the culture. However, it means there is no instant googling or google maps. Some advanced analog planning is necessary. Write down information you may need, print out vouchers, and make offline downloads to make sure you have all the necessary information with you or on your phone. Advance planning is required since you will not be able to search for your restaurant options as you are walking down the street. MAKE SURE TO DOWNLOAD OFFLINE MAPS! There will be internet. Limited, but available. You can purchase internet cards (2 CUC/ 2 dollars) at most hotels or ask you Casa hosts. Most hotels/ Plazas/ Parks are internet hubs. (some high-end airbnb homes now have routers) if you must, please buy these cards when you check-in at the hotel or casas. You will have to carry them with you so you can log in to use the internet when you encounter public parks/plazas.
Unless you have access to European bank accounts, you will likely have to figure out the exact amount you want to spend before your trip to Cuba. Havana food and drinks are generally cheap but you are on vacation...so make sure you factor in a lot of mojitos/ daiquiris you will want to drink. My advice to you is whatever you think you will spend, add another 300-500 dollars because you can always bring the cash back but you cannot take out cash once you are in Havana.
If you have a chance to travel to abroad, I would definitely save your foreign currency (EUR, GBP, CAD). Even though USD to CUC (Cuban Dollar) is pegged at a 1 to 1 rate, the US dollar has a 10% penalty charge. So if you are travelling to Europe before your Cuba trip, make sure to save some so you can exchange them to CUC in Havana. In general, you will have to pay a 3% commission to exchange money. For US dollars, that means you are getting 87 cents per dollar once the penalty is included while you will only have to pay 3% for EUR/GBP/CAD Your casas will sometimes have better rate than the bank. We have found that some hosts offered better rates than the bank because their relatives live in the US or they have some sort of US connection. Check with your casa host to see what their exchange rate is Mark CADECA or bank locations on your offline map. CADECA are the cash exchange places for tourists. Their rates are pretty similar to banks. You will need your passport to exchange money.
You can find taxis waiting for customers on the street anywhere. Most taxi drivers will know exactly where you are going since you will likely be going to touristy places. Taxis should cost you CUC 7 to 10 to Vedado and 10 to 15 to Miramar. Make sure that you negotiate and settle on a price before you get into a taxi.