I recently had this tour, 20th June, 2011....turned up at Deac Terr and had to ask a few people hanging around if this was it, I would suggest a badge or something for the tour guide. Anyway, great tour, very knowledgeable guide, great value for money since it was 1/2 price, but I did notice if you turn up and offer to pay, it is the same price £7.50, approx 2200huf.
The tour is a wlking tour, quite a lot of walking and some steep steps up to Castle Hill, comofrtable shoes is recommended.
My only negative is that the tour was 2.5hours and not 3.5hours as stated and the guide seemed to be in a bit of a rush to get away instead of staying and chatting, however there is plenty of opportunity throughout the tour to ask questions, advice or recommendations.
Overall, good value for what it is. If your fitter I would definitely recommend the cycle tour instead, Pest is completely flat, until you get to Buda where the climb to Castle Hill would be ermmm sweaty! :-)