Vulgar Latin is quite hard to study because people didn't write that down. They wrote a written language approximating Classical Latin, which was just the language of Rome around 100 BC, and probably also just the prestige dialect of the patricians at that time.
What people actually spoke in daily life was... different.
First there is the huge influence of Greek and the languages of the peoples the Romans conquered.
Then, one has to consider that the immigrants coming to Rome (forced or otherwise) had to learn Vulgar Latin as well, which always contributes tendencies to simplify.
Ultimately, people were probably fine talking to each other in a mix of languages, both each using a separate language, or by forming creoles, as long as they got to understand each other. Records and contracts then got written down in Latin.
What people actually spoke in daily life was... different.
First there is the huge influence of Greek and the languages of the peoples the Romans conquered.
Then, one has to consider that the immigrants coming to Rome (forced or otherwise) had to learn Vulgar Latin as well, which always contributes tendencies to simplify.
Ultimately, people were probably fine talking to each other in a mix of languages, both each using a separate language, or by forming creoles, as long as they got to understand each other. Records and contracts then got written down in Latin.