Does anyone know the minimum for the front rotors on an 03 Expy. Yes,I know its stamped on the rotor but its real rusty and I am not able to see anything.

 

Basically, if you can't read the spec cast into the rotor, it's time to replace them. The rust that obliviates the stamp has also attacked the internal webbing of the rotor. If you get it machined, it likely will cause a pulsation concern in very short order.
Any good shop that can machine your rotors will have access to the minimum spec. info. If they don't have access to that spec, find another shop.
You will likely find that the rotors are worn to the point that they cannot be machined.

 

For 2000's it was 27.7mm.