We go here every week. We actually bypass at least one closer park in favor of Washington Park. The reason being the people and their dogs. A great mixture of dogs we have also gotten to know several of the owners. We go weekend mornings, and there has never been less then twenty other dogs there. That is the most important thing for us, as we want our dogs to play and have fun which they always seem to do.
It is a big open space, some trees two water stations, and plenty of waste bags and garbage cans. I do have to agree there are generally quite a few cigarette butts around. There is also always plenty of tennis balls for the dogs to chase. (Do not pick them up, they tend to be urinated on quite a bit.)
It is a nice place to meet people who love their dogs as much as you do.