In May it still depends on how much snow is where. If you don't mind not being able to complete some trails, you may be able to get through at least some of some of the higher ones. A lot of stuff doesn't start opening until June-ish, but there will DEFINITELY be some stuff to check out. China Wall and The Gulches are open year round. There will probably be some snow patches and stuff, but that's part of the fun. That time of year is when this page will start being updated:
^ is updated by the public as people start filtering onto the trails, so keep your eye on that too. You'll be playing it by ear, just like we are.