There's a Petsmart near me that does boarding, it might be just day boarding for working 'parents'. Make sure you go and look at the place before you put doggie in it for boarding. When I at a Petsmart visiting a friend, the facilities it was pretty bad - dogs were kept in cage not runs. The cages were a bit bigger than just fitting and the cages were piled on top of each other. Dogs were put into rooms for exercise not runs. The dogs, in the rooms could walk around but defnitely not big enough for them to romp or roughhouse with a toy. This particular PetSmart boarding has NO outside runs at all. If you want to compare with where you thinking of going, the one I visited once is in Brick NJ.
I have two dogs and a cat. I know how hard it is to board, financially and emotionally. And we have a Mastiff that's huge like your Saint is huge. I'd get a place with indoor out door runs for doggie's sanity being caged.
at 9:09 AM on Oct. 1, 2009