Comment Survey method - old nokia (Score 1) 140
For survey purposes i would suggest finding an old nokia (3310 or similar) or some other phone that can have monitor mode enabled (or service menu). It is best if you would be able to slurp the data out of the phone via a cable but spot checks every 5-10 m would be OK (repeat at a minimum of 3 times).
Probably there is a better way but this is the cheapest and fastest way. For more ideas i'd suggest contacting OpenBTS/OpenBSC (as projects for ideas) or Harawd Welte / Dieter Spaar (as persons).
I would not suggest using 4G though (it seems a little bit too spotty and ureliable) if you can get your hands on some MiFi devices it would be better.
Next best option (or even better) would be WiMax (though it depends on availability).