According to the websites for the bridges, tunnels and the truck ferry, You cannot bicycle across the border between Detroit and Windsor. One option for the bridges seems to be to use a cab.
There are 2 ferries north of lake St Clair, one in Walpole-Algonac and one in Marine City that take bicycles and even have rates listed for bikes.
I am planning a bicycle trip around Lake Erie this summer and the detour around the Detroit crossing is adding a lot of extra miles.
If you need the web addresses for the ferries, I can locate them.