You have got some really great choices there!
Tusker House (L) - Have not been since rehab
This was one of the big surprises of our last trip. I'm not normally a fan of buffets, but made the ADR because we wanted a sitdown lunch at AK and at the time, the
DDP status of Yak & Yeti was still uncertain. The food was really good! Reminiscent of Boma, but better suited to my tastes, with less creamy, cinnamonny, gingery flavors and more spicy/tangy tastes.
Plaza Restaurant (L) - On the fence with this one
This is a favorite with my kids. The food was very good and very LARGE, and we very much enjoyed it for the simple menu and amazing ice cream desserts. We won't be back right away because there are still a few new places for us to try at MK, but we will be back eventually.
Sci-Fi Dine In (L) - On the fence with this one
This is one that I enjoy for the atmosphere more than the food. It was one of only 2 sitdown meals we had on my very first Disney trip, way back when I was a teen, and I just had to plan it once for my family because it is so unique. The menu is less than impressive and the food is just okay, so it isn't something I'm in a hurry to do again, but it is well worth doing once.
Teppan Edo (L) - Never been
Kona Café (D) - Been a long time
These two are tied as DS's favorite Disney restaurants, for completely different reasons!
Teppan Edo is a good quality teppanyaki style restaurant, not terribly original if you frequent such places where you live, but since we don't have anything like that here it is a must-do. The kids love the show, and the food is original but still simple enough that I wouldn't hesitate to bring even a picky eater there. It is a must-do for our family that makes it into the plans for every trip despite the number of Epcot restaurants we've yet to try.
Kona Cafe was some of the best food we've had at Disney on two trips in a row. We're all fish & seafood lovers, so the menu has a lot of appeal and we've never found the execution to be less than excellent. It has been over a year since our last Disney trip and DS11 is still talking about the giant shrimp on the shrimp & scallops entree there! Another must do, for a family that doesn't do many repeats. An early dinner there before hard-ticket parties has become tradition now, and we'll be back on our
MNSSHP night in September.
Narcoossee's (D) - Never been
At this point, I'm kind of feeling like I never give a bad review (really, there are a few Disney restaurants I don't care for, you just don't have them on your list!), but again this is one we really enjoyed. DH & DS are big lobster lovers, and although I don't care for lobster, I found the rest of the menu very appealing as well. The almond crusted cheesecake is to die for! And yep, this is another one we're going back to on our next trip, though mainly because my mom is joining us this time and she's never been.
Yachtsman (D) - Been a long time
We enjoyed the food, but of the signature restaurants we tried, this was the least impressive. The service was top-notch and the food was very good, but the overall experience was lacking that special something that the other signatures had. Because the atmosphere is so subdued and the decor so steakhouse simple, it just doesn't have the same "Disney" feel as Narcoosees or California Grill, and because the food is similar to any high end steakhouse we go to anywhere we travel, Yachtsman didn't make it onto our must-do list.
California Grill (D) - Been a long time
Another one that we really loved. I really couldn't say how much of it was for the food and how much for the magical experience. We had a fireworks-time reservation, got a window table, then DD was picked to "start" the fireworks and got a certificate and photo of her magic moment. The food was very good as well, one of the best California rolls I've ever had, so good that I almost didn't mind being pregnant and thus relegated to non-raw options, and an amazing pork dish with goat cheese polenta. And the molten chocolate cake with the seasonal sorbet, which at the time was orange for the perfect blend of rich, sweet chocolate and light, tangy citrus.

This one is on my Sept ADR list too, and I'm really looking forward to indulging in some more exotic sushi and trying that wonderful dessert again with whatever the seasonal flavor of the fall is.