The cost of replacing the prv is a small one. But you might want to just try and clean the filters on the PRV. In addition, you probably need to clean all the filters on the faucets. If your piping is copper, there's probably nothing wrong with it. As Jennifer says, the only time copper goes bad is when there is a galvanized nipple on the main line. The galvanized can clog up, but if you remove it, you should have good pressure again.
So, check the strainers on the Pressure Reducing valves, check the aerators on the faucets, and if your pressure is below 65 PSI, remove the Pressure reducing valves. They exist only to lower the pressure in high pressure areas. Many areas loose pressure over 30 years due to the additional use by multiple home projects. Though they start out as over 80 PSI, they can drop down to 50 PSI, then a PRV just becomes a hinderance.