Denver, Colorado.
A few years back we had Mayor Wellington Webb, who was a great proponent of landscape architecture and made a great push for a green ring along the Platte. Northside Park, 16th street Mall, and historic Olmstead designs. Plus, it’s home to UCD’s Landscape Architecture department- an excellent resource for visiting students. Nearby is Boudler for a study of walkable Pearl Street, and the foothills of the Rockies, for a study of outstanding State and National Parks. And, unlike some of those larger Cities you mentioned, you can kind of see it all in just a couple days.