I've seen both Groundhog Day and Sunset Boulevard, and I highly recommend both.
At present, there seems to be a lot of public good will and appreciation for Andy Karl's "the show must go on" work ethic in the aftermath of his recent injury, so demand may be somewhat higher right now for Groundhog Day (not sure what the rush/lottery situation is like with that).
Sunset is nearing the end of its run and the Palace is a high-capacity theater, so you will likely be able to get good seats at a reasonable price. I seem to recall reading around here that rush tickets are readily available.
==> this board is a nest of vipers <==
"Michael Riedel...The Perez Hilton of the New York Theatre scene"
- Craig Hepworth, What's On Stage