  We analyze the constraining power of future dark energy experiments for
Pseudo-Nambu Goldstone Boson (PNGB) quintessence. Following the Dark Energy
Task Force methodology, we forecast data for three experimental ``stages'':
Stage 2 represents in-progress projects relevant to dark energy; Stage 3 refers
to medium sized experiments; Stage 4 comprises larger projects. We determine
the posterior probability distribution for the parameters of the PNGB model
using Markov Chain Monte Carlo analysis. Utilizing data generated on a $\Lambda
CDM$ cosmology, we find that the relative power of the different data stages on
PNGB quintessence is roughly comparable to the DETF results for the $w_0-w_a$
parametrization of dark energy. We also generate data based on a PNGB
cosmological model that is consistent with a $\Lambda CDM$ fiducial model at
Stage 2. We find that Stage 4 data based on this PNGB fiducial model will rule
out a cosmological constant by at least $3 \sigma$.
