Stab a hole in the exhaust. Listen when the shift changes happen. Hey, it's a free mod if you are absolutely against buying a scangauge (which is the best idea here). A OBDII blue tooth connection is also a lot cheaper and can connect to your phone as well.
A modern smart phone can tell you your MPH if your speedometer is also not functioning.
http://www.amazon.com/Small-Elm327-O.../dp/B005M1AVFQ
This option won't be as nice as a dedicated scan gauge, but it will still give the same data points.