The traffic is not so heavy. At least if U compare it with other countries. The street with heavier traffic in Vedado, Havana, for example, is 23rd. But don't worry, U can drive without problems, many tourist do it. I used to go usually in bicycle everywhere in Havana without problems. The worst time is [in morning, of course] and in the afternoon between 3 and 6pm. In the pic U'll see the streets U asked for.
Also the naming of the streets in various neighborhoods of Havana like Vedado, Miramar and Playa is easy. Starting from 23, the parallel streets going in the sea directions decrease the number and are only odd numbers. In the other direction they increase. The perpendicular streets are named by the letters of the alphabet so starting from G going to the sea the next letter is H and the next one is I where the casa U choose is located. In the other direction the previous street of G is F. The letters start from Paseo street, where I used to live. Away from Paseo the naming of the streets change to even numbers....is really easy ;)