  We critically examine the constraints on internal angular momentum transport
which can be inferred from the spin down of open cluster stars. The rotation
distribution inferred from rotation velocities and periods are consistent for
larger and more recent samples, but smaller samples of rotation periods appear
biased relative to vsini studies. We therefore focus on whether the rotation
period distributions observed in star forming regions can be evolved into the
observed ones in the Pleiades, NGC2516, M34, M35, M37, and M50 with plausible
assumptions about star-disk coupling and angular momentum loss from magnetized
solar-like winds. Solid body models are consistent with the data for low mass
fully convective stars but highly inconsistent for higher mass stars where the
surface convection zone can decouple for angular momentum purposes from the
radiative interior. The Tayler-Spruit magnetic angular momentum transport
mechanism, commonly employed in models of high mass stars, predicts solid-body
rotation on extremely short timescales and is therefore unlikely to operate in
solar-type pre-MS and MS stars at the predicted rate. Models with core-envelope
decoupling can explain the spin down of 1.0 and 0.8 solar mass slow rotators
with characteristic coupling timescales of 55+-25 Myr and 175+-25 Myr
respectively. The upper envelope of the rotation distribution is more strongly
coupled than the lower envelope of the rotation distribution, in accord with
theoretical predictions that the angular momentum transport timescale should be
shorter for more rapidly rotating stars. Constraints imposed by the solar
rotation curve are also discussed (Abridged)
