The United League division of the North American League will be running its pay-to-play developmental, winter instructional league in Harlingen Texas during February. The stadium in Harlingen is the home of the Rio Grande Valley WhiteWings.
This recent article mentions that managers and coaches from other independent leagues will be on the staff, and the TWL mentions which MLB organizations are sending scouts to grade the players:
There are several good books about the independent professional baseball leagues. You are welcome to see a list of suggestions through this link: Books Get notified of upcoming independent baseball tryouts from either of these services: first service or the second service. Prospective players can find some helpful resources here We will be providing a growing list of possibly helpful tips and suggestions on various baseball information. This will range from "how to" information about baseball skills all the way to helpful information for casual baseball fans. Please click the link for more information: Tips And How To Information