I can't find my pressure reducing valve and am not sure if my house even has one. I checked for several feet around the water meter and for several feet before my main water lines enters my house. The rest of my main water line runs underneath my driveway. So I want to know, if putting one just after the water meter box would still be able to fix my water pressure problem?
Yes you can add additional PRV or regulators. The only possible side affect is a reduction in flow as they usually have restrictions. I have machines that I use 2 regulators one to do some basic isolation from the heavily fluctuating main air down to a fairly clean 90 psi then a second to provide a rock solid 80psi. And this machine runs great with no mishandling like that so Yes get the pressure down to what you want.