've taken up the tile in my kitchen. I want to just stain the cement floor. I'm having trouble getting the old mortar up. Any suggestions?

How about this?

Concrete Polishing, Diamond Polished Concrete, Stain & Polish Concrete Service, Warehouse Flooring

Actually, you can rent some machines from Home Depot that will remove stuff, but definitely not as spactacular as the above.

Also, not sure if you want to epoxy paint it.