My friend at SLCGOV probably only has jurisdiction over the parks on this list (which unfortunately excludes the county parks, such as Creekside or Crestwood and any other parks further south): http://www.slcclassic.com/publicservices/parks/list.htm . Also the 'Natural Areas' on that list may be off limits because of their ecological significance, but I was wondering about Jordan Park (33.5 acres) or Parley's Historic Nature Park (87 acres). Check out the pictures, they look promising in terms of challenging landscapes, particularly Parley's has a lot of land and challenging topography. I'll check it out myself this weekend. Any other park on that list you think might work as well? I will definitely suggest Fairmont too besides the aforementioned ones.
I have an official meeting with her the morning of Friday April 20th and will know more after that.
Again, don't spread the word beyond this community yet, and please DON'T contact the city yourself at this time! Thanks!!!