Personally, I don`t trust pretty much any of the geiger counter data coming from the hands of the average guy out there.
Most of the radiation counters out there in the average person`s hands are the cheapest of the cheap and very poorly calibrated. If you check the documentation included with them, they always tell you to calibrate with a known source. Medical and educational centers will often offer this service, but... I have yet to hear of anyone actually doing it. They pop the batteries in and are on their way. This is why you`ll see some drastically differing figures between people in the exact same locations. The lower quality the counter, the less chance they bothered to even do the most basic calibration before sending it out.
I`ve encountered one that told me I was emitting 3μSv/hr just standing there, which would have been pretty horrific had it been true. (Proper calibration made it much more realistic...)
I agree that there is going to be higher radiation in dust and such on the ground than in the air - I am hesitant to just take anyone`s word for just how much. Having seen the wonderful quality and accuracy
of the low-ish cost devices sold like crazy after the tsunami, unless they can say they had it calibrated and tested at a university or medical center, I`ll just stick to the measurements taken by universities and official centers.