what are r22 freon guages going to read if the evaporator coils in the air handler are dirty

That really depends upon to many variables. A actual physical look and see is the correct way to check for dirty coils. many Many times the suction line will frost up from liquid refrigerant passing thru the coil but that could be caused by other items as well.

I learned never to guess at a coil being dirty or not. Just cut a hole or get an access on the air into side and see for sure.

All 3 A/C evaporator coils are cleaned in this house every 2 years since I do not like the dirty socks smell.