Well i hate to say it but it's not a safe city. But as long as you mind your own business you should be fine. At night if your by yourself I might lock your doors at stop lights as people have been known to jack your sh!t at a red light.
For the most part there is no real 'downtown' there is cobo hall, joe louis arena, the GM building and stuff right on the water, but there's nothing really too do as far as foot traffic. there are little pockets of areas that are cool around the city, like Belle Isle, and some of the border cities are cool like Birmingham, pleasant ridge, ferndale, royal oak.
The nice thing about the area is the access too outdoor activities. Any sport or pastime you can think of you can do, except for surfing.
too bad about the weights, theres a big powerhouse downtown. Bodyweight excercises are cool though, they're harder than people think.
Your right across the border from windsor ontario, very cool city, lots of concerts/festivals during the summer.
If I didnt cover something else you would want too know dont hesitate too ask, and once you find out exactly where your going too be you can let me know and I'll give you some stuff too do around your area, if that would help.