My dogs love to swim here in the leash free area designated for dogs. If you don't want to be near dogs, stay as far east as you can. For those with dogs, stay west.
On weekends in the summer, this place is crazy busy, but my dogs don't mind waiting until after 7pm to go for a swim.
As others have mentioned, do not park on the grass, you can get a ticket. Better to wait for a spot or don't go during peak hours on the weekend.
A great park and all the regulars are really good about picking up after their dogs... especially compared to other leash free parks. There will always be those who don't do the right thing but at least here, the majority are responsible dog owners/walkers.