I have done one in front of my house. It is only about a 10ft curved wall for a flower bed. It took about 9 hours with one person. This wall is about 3 times as big.
I will also have 2 people on the job site working. So if I take the 9 hours x3 and divide that by 2 it comes out to 13.5 hours.
What's your thoughts on that versus dividing it by 2?