  We present a detailed analysis of 317 $2.0 \leq z \leq 2.7$ star-forming
galaxies from the Keck Baryonic Structure Survey (KBSS). Using complementary
spectroscopic observations with Keck/LRIS and Keck/MOSFIRE, as well as spectral
energy distribution (SED) fits to broadband photometry, we examine the joint
rest-UV and rest-optical properties of the same galaxies, including stellar and
nebular dust attenuation, metallicity, and star formation rate (SFR). The
inferred parameters of the stellar population (reddening, age, SFR, and stellar
mass) are strongly dependent on the details of the assumed stellar population
model and the shape of the attenuation curve. Nebular reddening is generally
larger than continuum reddening, but with large scatter. Compared to local
galaxies, high-redshift galaxies have lower gas-phase metallicities (and/or
higher nebular excitation) at fixed nebular reddening, and higher nebular
reddening at fixed stellar mass, consistent with gas fractions that increase
with redshift. We find that continuum reddening is correlated with
$12+\log(\mathrm{O}/\mathrm{H})_{\mathrm{O3N2}}$ at $3.0\sigma$ significance,
whereas nebular reddening is correlated with only $1.1\sigma$ significance.
This may reflect the dependence of both continuum reddening and O3N2 on the
shape of the ionizing radiation field produced by the massive stars. Finally,
we show that H$\alpha$-based and SED-based estimates of SFR exhibit significant
scatter relative to one another, and agree on average only for particular
combinations of spectral synthesis models and attenuation curves. We find that
the SMC extinction curve predicts consistent SFRs if we assume the sub-solar
($0.14Z_{\odot}$) binary star models that are favored for high-redshift
galaxies.
