comfortable you would be. I'm pretty sure that the one I go to wouldn't mind because she would probably assume that you will buy at some point and that you might talk about the store/word of mouth..
Why don't you call and speak to the owner? I would ask if they have a Stitch & Bitch or coffee night and take it from there-you might feel more comfortable that way. I know at the SnB I went to last, most everyone brought their own stuff. Some bought, some didn't, and no one seemed to care.
Good luck! I know I love to go sit at mine and knit. Yes, I do drop $ in there, but sometimes I just knit.