Would a power washer work?
You could try etching with muriatic acid but you must be very careful with both ventilation and exposure to skin. I will do this prior to pressure washing and painting a concrete surface. You may have to do it a couple times to lift everything off. Wet the surface with a garden hose, then pour the acid onto the surface. It will react by bubbling and smoking, releasing a vapor that you want to avoid inhaling. Once that reaction slows you can scrub with a stiff broom or a wire bristled brush. Then either pressure wash or rinse with the hose to see what progress you've made. Any home improvement store will carry muriatic acid in gallon jugs. Good luck!
Power wash it in a angle spray after you put some stripper on it, but try power washing it first, Amador
Looks like this post is a few days old, but maybe you have not completed the project yet. Depending on the age of the home, you need to be careful about what kind of paint is on the surface. Take extreme caution if you suspect the paint contains lead. Visit the EPA site for information about lead paint and follow guidelines for lead safe practices.
You are most likely going to need to strip the paint. My favorite product is Dad's Stripper. It's available at Ace Hardware. It is very strong and will burn your skin and the fumes are not pleasant. Once you get all the paint removed and disposed of properly, you can repaint or coat the surface or leave it natural.