I was told one time that at a u-17 ecnl game there were close to 80 coaches on the sideline. In that case i can agree with you that they will find you. Im sure the u-16 may not have as many on the sideline and i know the u-15 do not. The u-15 age may be a good time to make that initial contact with a coach to let them know who you are and where you are at so they do not have to find you.
Think about this. At the u-17 age you are past Sept 1st of your jr year when coaches can officaly contact you. If they are just now finding you then it may be to late. u-16 girls in the fall are playing their final club season before the coaches can contact them. That season is the last chance a coach can see them play before they start contacting players about coming to play for them. the u-15 girls are at the right age to get started getting their name out there. You have to remember that some u-15s are already soph in high school and in the same boat as the u-16s. I would not wait to see if a coach finds me and i would help them find me.