Hi I'm a first year at a T30, almost done with the first year. Here's my two cents:
Its not a good preparation. Perhaps the princeton name might carry some weight but you're still strictly better off getting a masters in econ from places like LSE/Duke/Wisconsin etc. Check with the MPA director at princeton what books are followed for the econ courses. Ideally it should be something at the level of MWG for micro, hayashi for metrics (macro varies you have to worry about that later). I'm 95 percent positive that the courses are not taught at that level and obviously adcoms will know that which will hurt your admission chances, not to mention your actual performance should you go for phd.