I think "Deep Creek Volunteers" is the best name. It sounds informal yet organized, with the selfless goal of helping the place. I think a sign or brochure box at the beach crossing point would be great. People approaching the place can at least be exposed to the proper etiquette at the springs regarding trash and behavior. An email list is also really important for you guys to coordinate trash days or to communicate any other newsworthy item. Probably the best thing is to set aside a few days a year where everyone gets together at the springs under the Deep Creek Volunteers banner and picks up trash and informs visitors of the etiquette to the place. Great work, volunteers!