We've been lucky to get a tour for just two of us, and we really enjoyed a ride in old town and Mala Strana. Our guide was Anna, and we didn't have any problems in communicating in English. First, she taught us how to ride a Segway (really easy), then we took 2-hour tour and Anna managed to show us some places we haven't been before (although we lived in Prague for 3 months at that time already).
We'd highly recommend to take this kind of tour to anybody. Keep in mind that you can create your own travel loop to visit the places you're most interested in.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.