I own a Jet, and have been happy with it, and I have been extremely impressed what I have seen of Grizzly jointers. I had a chance to use one of their 8" models, and thought that the quality, as well as fit and finish were exceptional. I would not hesitate to buy one of these.
I think you have a good chance of getting a great deal at the show. I bought my jointer that way, and other tools that way as well. What I would suggest is getting there as early as possible, and work out a deal right away, and pick it up at the end of the show. They might even throw in a new set of blades for you, even though the wear from the show will be minimal to say the least.
Regarding the Harbor Freight jointer, I would be cautious there. It depends on what you plan to use it for. If you will be using it only for face jointing boards to get a flat surface prior to planing, then this might be a suitable option. If you plan to use it for edge gluing boards, then I would stay away from it. Their jointer does not have a reputation for carrying the level of precision that you will want for this operation, and I have heard they are difficult to tune. Of all the power tools I own, the one that I place the most scrutiny on for precision is the jointer. What passes for "good enough" in many tools, does not cut it on a jointer. I would rather have no jointer than have a marginal one. In the absence of a jointer, you can use other means of edge jointing lumber, such as router table, hand plane, good table saw blade/fence, etc.
Good luck with the jointer purchase. You are going to love this, and you will use it even more than you think.