  Supersymmetric grand unified models based on the gauge group SU(5) often
require in addition to gauge coupling unification, the unification of b-quark
and $\tau$-lepton Yukawa couplings. We examine SU(5) SUSY GUT parameter space
under the condition of $b-\tau$ Yukawa coupling unification using 2-loop MSSM
RGEs including full 1-loop threshold effects. The Yukawa-unified solutions
break down into two classes. Solutions with low tan\beta ~3-11 are
characterized by gluino mass ~1-4 TeV and squark mass ~1-5 TeV. Many of these
solutions would be beyond LHC reach, although they contain a light Higgs scalar
with mass <123 GeV and so may be excluded should the LHC Higgs hint persist.
The second class of solutions occurs at large tan\beta ~35-60, and are a subset
of $t-b-\tau$ unified solutions. Constraining only $b-\tau$ unification to ~5%
favors a rather light gluino with mass ~0.5-2 TeV, which should ultimately be
accessible to LHC searches. While our $b-\tau$ unified solutions can be
consistent with a picture of neutralino-only cold dark matter, invoking
additional moduli or Peccei-Quinn superfields can allow for all of our
Yukawa-unified solutions to be consistent with the measured dark matter
abundance.
