I am by no means an expert, but I was told not to grout a deck b/c of frost heave. That being said, we have a patio now with the stones set in concrete that has much the smae effect, I think, as a grouted pation. It has held up fine to our upstate NY winters. The only real problem is a couple of smaller stones have come un-stuck from the concrete and we have to set them back in their spots. (The patio was in when we bought the house, so I don't know a lot about the installation).

Oh, I should mention that even with the concrete under and between the stones, little weeds manage to take root in any little, teeny, tiny crevices they can find.

Thanks for your response Carajon. I went to two different Stone and Masonry stores today. One store recommended "Sand Joint Stabilizer (Prosoco) which goes over the bluestone and sand in your joints and "seals" it. The second place gave me a brochure for "Stabiliz-O-Block (Sable Marco) which is the actual Polymeric Sand for paver joints. I'm going to investigate both. Oh.. and BOY is Bluestone expensive.. eeek.