Clark Park in Mexicantown is a good bet.

They just announced plans in concert with the NHL/Winter Classic to do a complete makeover of that rink, complete with a free zamboni, other upgrades.

If we get a few solid weeks of single digit nights, and no days above 32, [[which looks possible), the canals on Belle Isle will freeze and those make for fun pick up spots.

http://blog.clarkparkdetroit.com/?p=298