Yes, he spoke Greek as well as Latin. Most educated Romans at the time spoke Greek, although Latin was the language of Rome.
Julius Caesar spoke Latin during his time as a prominent figure in ancient Rome.
the commoners
Antony
Casca.
He asks permission to speak in the funeral of Julius Caesar.
To explain the reasons for Caesar's death
Mark Antony says it in Act 3 Scene 1 of Julius Caesar, just after Brutus has given him leave to speak at Caesar's funeral.
Julius Caesar spoke Latin. He is also known for the excellence of his Latin prose, which is still read by students of Latin today. He would have delivered speechesand written in Latin but Latin was considered a second 'formal' language even then. Amongst friends and family he would have spoken a kind of lower, colloquial Latin more like modern Italian. Unfortunately, we know very little of this language (not surprising considering as it was almost entirely non-written) what we do know is mainly gathered from graffiti!
Caesar spoke Latin during his reign as a Roman leader.
Julius Caesar grew arrogant near the end of his life. All the honors and power he accumulated "went to his head", so to speak. The conservative Republicans saw this as a first step to a monarchy with the power of the Senate and the people negated.
The language of Ancient Rome was Latin, however educated Romans spoke Greek, so amongst the patricians, Caesar would have spoken Greek. In fact, when he died, he is believed not to have said "Et tu, Brute," but instead "καὶ σὺ τέκνον," which is Greek for "Even you, my son?" (Brutus was not actually Gaius Iulius Caesar's son, Caesar used it poetically.)
When at war, Julius Caesar was known for his quick action. Although he planned things out before hand, he could also throw away the game plan, so to speak, and order quick last minute changes. He was also the first and probably the last Roman general to have centurions present at his planning meetings and to listen to their opinions.