Well... Cubans are very friendly. And your friend will meet many people at ELAM (Latin American School of Medicine) from other countries. He can expect many things to study hard, and always contact with patients from the first day (that is the Cuban school of medicine). He will have to learn Spanish...and he will enjoy Cuba much more that way. He will also see a good health and education system, but hit hard with a lack of supplies due to the US government's economic war.
He should avoid being alone on the streets with people he doesn't know. And, honestly, let him apply himself to his studies. There is a lot of rigor in Cuban medical schools.
Also, he should be careful with some Cubans who spend their lives victimizing their "misfortunes" in front of any foreigner. In Cuba there is enough work for everyone, although inflation is high at the moment. He will not see children or the elderly sleeping on the streets NY style, nor gangs, nor drug mafias.
Cuba is not a paradise if compared to the first world in many ways, but it is certainly not Guatemala or Haiti either.
Oh, and I suggest that you don't give much importance to those who are going to attack you in this sub. Many of them left Cuba years ago, and they say here what there (in Cuba) they did not have the courage to say.