You have to use a few things:
- Street Names
- Parts of the city
- Look at the picture background for what the buildings look like
- Occupational cues about the owner
- Landmarks
For example, the text message says you're stealing a comedian's car. It should be around the Comedy Club. When they only give you a part of the city, look very close at the picture to find out where the car is and if you can spot any distinct architectural features of the surrounding buildings. The second car was the hardest for me (looks like Bentley's sports car).