To find the average population growth per year, divide the total growth in population over 2 years by 2: 600 people / 2 years = <<600/2=300>>300 people per year.
To find the projected population growth over 5 years, multiply the average annual growth by the number of years: 300 people/year * 5 years = <<300*5=1500>>1,500 people. Answer: \boxed{1,500}.