The Radisson Hotel is on South Temple, and the Sheraton is on 500 South ("5th South" in Utah parlance); so the Radisson is five city blocks north of the conference hotel. The Radisson is also about a block further west than the Sheraton, so you'll have to walk 6 blocks. Salt Lake City blocks are bigger than normal though (660 feet per side and exactly 10 acres per block), so that's right at three quarters of a mile. Depending on your pace, 15 - 20 minutes should work. The terrain is fairly flat, so you won't have to worry about any drastic changes in elevation.
Downtown Salt Lake City is safe; although, like any metro area, it does have some problem areas you will want to avoid. The immediate area around the Radisson is very safe. The hotel is adjacent to the Salt Palace Convention Center. Just a block to the west is Vivint Home Arena (where the NBA Utah Jazz play). The Gateway area is just one block further west. The Gateway area used to be a very popular shopping area and houses the Olympic Legacy Plaza--from the 2002 Olympic Winter Games. There are some restaurants in that area, but it is in a state of transition right now, and I'm not sure how interesting it is anymore. I think if I were walking in Salt Lake City at night, I'd head east.
To the east of the Radisson is Abravenel Hall, home of the Utah Symphony. It's a gorgeous concert hall, but unfortunately it doesn't look like the symphony performs until later in June this year. Just east of Abravenel Hall is City Creek Mall, which is often maligned on this board, but is in fact a very safe and pleasant place to stroll, people watch, and window shop. In the summer, there is a small splash pad where kids play and a nice fountain that "dances" to music. There's a creek (City Creek) that runs through the middle of the mall, and one can see trout swimming in the clear water. There are several Church sites in the area to the north of the mall: Temple Square, the Joseph Smith Memorial Building, the Church Conference Center, the Family History Center, the Church History Museum, and and several other Church sites.
Finally, you should know that the Sheraton is a couple of blocks east of the most "notorious" illicit drug area in the city--Pioneer Park. Salt Lake City and the State of Utah have made a concerted and combined effort to clean it up in recent years, and it seems they are having some success; however, my impression is that the process is still a work in progress, and I would not walk there at night.