Costs aside, you can easily convert to 15" wheels/tires without issue.
According to Tirerack, the Protege was equipped with 205/45-16s. If you go with 15" wheels, go with 195/55-15s. The conversion will make your speed error less than 1% too fast, which means that when your speedometer reads 60 MPH, you are actually travelling at 59.5 MPH, a negligible difference, and well within the 2% rule that most wheel/tire installers use when changing wheel sizes.
Plug the Protege into the tire finder at Tirerack, and they'll give you a lot of inexpensive choices for quality tires, both in 15" and 16" sizes. I've used them for years without any problems or surprises.