Forza Horizon 2 is due at the end of September, but you can go for a test drive a little earlier.
Microsoft has announced a demo is coming on September 16. The announcement promises a handful of cars to explore the European landscape with, but doesn't detail just which hot rods you'll be handling. The company also released the full list of Achievements, for any hungry Gamerscore hunters out there.
Forza Horizon 2 is coming on September 30.