Hi Mermaid!! Hope you enjoy your stay here!! The leaves are just starting to change so it should be really pretty for you!
First off, the Westin is great. You won't be disappointed.
As for restaurants: regarding some of the previous posts - "Oh So Good" is closed - they relocated to Elgin St. and are no longer in business to my knowledge. As far as Canal Ritz goes, we have a very different opinion - have eaten there 3 or 4 times trying to give it yet another chance and I'm sorry to say, we have never enjoyed a meal there. Although the view is very pretty.
Here are some places I would suggest: For casual dinners downtown or nearby: The Keg, Black Tomato, Mama Grazzi, Maxwell's, Big Daddy's Crab Shack for yummy seafood, Mukut for Indian
Finer dining: Domus, Kinki for Sushi, Restaurant 18
A bit further: Bella's on Richmond - excellent Italian, Bekta on Richmond, Coriander Thai, Papagus for Greek, The Works - over 80 varieties of burgers, Lone Star for tex-mex
For dessert - Memories downtown
Drinks - Vineyards (wonderful wine bar - can try by the glass)
Most of these places are either walking distance or a 10 minute cab ride from downtown.
Hope that helps. Feel free to ask if you want specifics about any of the above. Enjoy!!