Living closer to Puget Park Drive In than to Valley Drive In in Auburn, we routinely choose to go to Valley Drive In over Puget Park. Puget Park's prices have gone way up, such that it costs me $29 to take the whole family to Puget Park (six of us), or $18 to go to Valley Drive In. Even factoring in additional gas, it's a no-brainer. Valley Drive In is also in much better shape that Puget Park -- a comparison of the bathrooms alone should be enough to sway folks, because Valley Drive In's bathrooms and other facilities are very clean. Valley Drive In also has five screens (the sixth was closed down for some reason) to Puget Park's single screen, providing far greater variety.
If you live in Everett or further north, Puget Park is a decent trip down nostalgia lane. If you live anywhere south of there, however, make the trip down 167 to Auburn and Valley Drive In instead.