Not sure where the OP is living but several years ago DC United and US Soccer foundation partnered and converted a bunch of basketball courts to Futsal. These Futsal courts are throughout DC (NW too) and are under utilized or being used for something else completely; I saw handball being played by a huge group of folks last week for example. If kids would commit to playing pick-up and met at these courts around the same time period any day of the week, we could have a pick-up culture develop without ever worrying about the availability of fields.

Honestly I do not see much of this and partly its because fields are being used most of the time all year long.

Wish I could help.

When checking out some club websites I found that a few offer weekly pickup games during the summer. Maybe you could contact a few near you and see if they have anything.

Naive but genuine question: Where do 12-year old girls go to play pick up soccer in the DMV?
DD works with a private coach and works on skills on her own but she was asking to just play.

Basketball I could help her with. I only see grown men playing soccer on the open fields out here.

Thanks in advance.