acrylic is water based paint. If it is on concrete and most surfaces, the paint will just wash away with water, dish detergent and a scrub brush. The concrete has probably absorbed the pigment and will require acetone (fingernail polich remover)or a number of products such as Goo Off, Goo Gone or Taginator. Keep working at it it will come off or eventually fade to the point that you won't notice it.
Thanks! I'll try it tomorrow.