I haven't seen the PArking Lot Shakespeare group, but I have seen New York Classical Theatre's TWELFTH NIGHT in Battery Park, and the quality was first rate. (This is the same group that did HENRY V so well last summer.) The Malvolio/dropped letter scene was the best I have ever seen, very fast paced and funny.
Saw Love's Labour's Lost in 2010 and As You Like It in 2006. It's amazing what a good job they do given that it's, well, a parking lot on the Lower East Side. But that adds to its charm.