Calipers can seize after awhile and hold the pads against the rotor even when your foot is off the brake pedal. That would explain constant grinding noises. Brakes should not squeal unless they're down to the audible wear bars...that being the whole point, to alert you that the pads are low.
If a rotor is warped you will usually feel a vibration in the pedal when you're braking that goes away when you let off. Cheap rotors have a tendency to warp quickly.
Check the brake fluid level. If it's low, it can cause the light to come on. Also, your parking brake cables might be sticking on.
Don't give up! Brake problems should be relatively easy for a competent mechanic to fix. Sounds like your current place is not very good.