Fall is my favorite time of year here. It’s absolutely perfect. The mountains are gorgeous, especially in Park City, and the air is crisp but not really cold. You should definitely go up to the ski resorts and check out Old Town Park City. I grew up there, and used to work on Main Street, it’s always a great place to spend an afternoon. Temple Square is fairly interesting, just try to avoid the missionaries. They’re usually sweet young things with nametags. The Gateway Mall near the Energy Solutions Arena (former Delta Center) is a nice place to spend an afternoon, too. There are plenty of shops, plus a planetarium and a movie theater.
I love the Utah Museum of Fine Arts. It’s at the University of Utah, which is just a lovely campus anyway and has a pretty spectacular view of the valley. Definitely check out the Salt Lake City Library. It’s brand new and it’s gorgeous on the inside and the out. It’s worth a look. It’s pretty easy to get around Salt Lake between the TRAX train and the buses. Fare is free in the downtown area. And it’ll take you right up to the Fine Arts Museum at the U.
The Zoo is fun. They have a great little pavilion set up to view the elephants, and they’re new cat habitat is really cool. They also had the cutest little baby orangutan the last time I was there (I guess it’s been about a year and a half now).
The weather is pretty mild in the fall. If you’re here in Sept or early Oct it’ll probably even be hot. If you want to venture further into the mountains, you could take a drive up into the Uintah Mountains, which are just east of Park City.
Salt Lake is a good film town. The Broadway Theater and the Tower Theater are both excellent little art-house type places and they show the indie flicks and documentaries that don’t get wide release. There’s also a place called Brewvies, which is, as you might guess, a bar and a theater. They have pretty decent food and tables for your beer in the theater itself.
As for food, I would suggest Piper Down on State Street. It’s an “Irish” pub, and it’s just a great place to get a beer and some decent food. If you like clubs and live music, there are plenty around the city and there are usually shows every weekend.
If you’re going to be here in September, you might be in time to catch the Utah State Fair. Which isn’t the greatest fair ever, but hey, it’s not far from downtown and it’s usually got a few interesting things.