That sensor outputs fairly high impedance analog signals, the output
impedance is 32k or so.
I would use shielded cable really - just like for audio - better at protecting
sensitive signals. Multicore screened cables are commonly available.
If you stick with UTP then one pair for each signal (plus ground), one pair
for power (plus ground).
The ADXL335 suggests filter capacitors on each signal, for a long cable
run you want capacitors at the receiving end anyway to reduce EMI pickup,
so place the filter caps at the Arduino end if possible.