Yes. The workaround is to go to National, search for a city name, and click "See Enterprise locations." It will then patch you through to Enterprise with your National account.

This works somewhat smoothly for pickup at a neighborhood store where National doesn't have a presence. However, if you want to check Enterprise airports where National does, initially they don't show up. The workaround is to first search for a neighborhood store, and start the reservation path, then click switch pickup location, and type in the airport code.