If the only time you call your dog to you is to go home, try the 50ft leash & call her back every so often just simply to give her treats, to pet her or to play with her. She'll eventually start associating "come" with something she likes instead of ending all the fun when she has to come. This is what I've been doing with my dogs & it has worked great. I got this advice from a friend who is a trainer. Hope this helps you.

^I agree with that completely, your dog should feel that coming to you is more fun than just staying in the park, unless he feels it, he will continue to play deaf, and yes, they can be as stubborn as they want to be.

[rlang]

Training your dog to come is the most important thing to train them. It can save your dogs life (ie...running in the street). Clicker training your dog can be very rewarding with some work and commitment. This site does a great job on this topic Start Clicking | clickerworks.com

[Tidus&Me77]

I would train my dog by simply calling him and rewarding him with a treat.

simple, but effective.

[german sheep]

As long as your dog knows that he is getting everything by you why would he have a motivation to go away or not to come when called?

I go further:
A dog does not want to go away from me when everything is clear. Why should he? That would be against its natural.

Dogs who really have a serious leader don't need to go away. You always can check the hierarchy by how far the dogs go away from the owner.
Look at the photo below, I'm working with my dog Akir and my bitch Ondra is not more than just a jump away:

hose training Photo Gallery - Photo 15 of 15 by Cornelia Benford - MySpace Photos

[Lara's mom]

I have a border collie/spaniel X. She has always been VERY well behaved until about the last year. She has developed what I call "selective hearing." I can call and pretty-please her until I'm blue in the face! If she's involved in some interesting smell or playing with another dog in the park, she just doesn't "hear me."

I thought maybe her hearing wasn't so sharp anymore...However, if I say the word, "cookie" in just a slightly louder than normal voice, she is at my side in a shot!

[Bamber]

Hi,
So i agree with the above comment ::--::
Using a leash in a confined area is a great idea.
Normally a lot of dogs will not come when they are called because they no it ends the fun. * as you said she does not like to leave the dog park.. by coming to you, she knows that will happen.
A trainer once suggested to me to try calling the dog during their play time (even with a leash) and then releasing them to have more play time. Its always best to use an excited voice rather than a low demanding voice when teaching your dog to come!!
GOOD LUCK
dont get discouraged, its one of the hardest commands to teach

[Lara's mom]

Great idea! I'll try that!