According to what info I have the Saturn Ion for that year is not in the worst vehicles. The Saturn Ion 06 is, however.
Possible trouble spots are: Minor transmission problems, electrical issues 03, 04, 05, suspension 03, 04, Just going by the black dots... Funny enough the Ion for 06 has fairly decent marks in the repair frequency yet it is not rated highly as a used car.
Look here for reliability ratings and possible trouble spots...
http://www.edmunds.com/saturn/ion/2003/reliability.htmlWith all that being said and that low a mileage and if you can get a good price I think for a first car it shouldn't be a bad deal. Although, the car is about 8 years old so you may wind up with issues associated with a vehicle that sits a long time without running such as seals (AC in particular) and the rubber suspension bits being brittle. Could also have some fuel related problems sitting that long. You didn't find this in Pasadena did you? I'd also change out every bit of the fluids in it.