My 1.5 year old English Pointer has been playing at the park with a Boxer, Mixed Lab/Rott, and a Mixed herding type dog.

My first question is about the Boxer.  This Boxer is very friendly with a super temperment.  Our pointer is very submissive, but she is always biting at the Boxer's legs.  I am thinking this is because the boxer is about 30+ pounds heavier than our Pointer.  I think she does this to encourage the boxer to run with her.  There is no yelping or growling.  Is this just dog talk?  Should I try to stop this behavior?

My second question is when all the dogs are together.  The mixed herder is always getting these dogs into a group, of course.  But, our pointer always just flops on her back.  I figure this is just submission, and she is finding her place in the group.  All the same it drives me crazy.  At times, our pointer runs with her tail between her legs....is this a sign of fear?  Now, our pointer can EASILY out run the others.  The problems sort of rise when they end up grouped into a cluster instead of running the park.

Thoughts?

It's almost impossible to answer these sorts of questions without actually observing the dogs in action, as there can be so many other factors which influence behaviour.  If she's persisting in this behaviour, and it's something other dogs may not appreciate, then I think you should distract her from it, before it becomes her coping stratagy :(

The tail between the legs is normally the sign of a dog who doesn't want anyone to notice it's presence - your dog is an adolescent who isn't yet confident enough to mix freely with adults, so she's hoping they won't notice she's there - very good dogggy protocol ;)