Vibrational wave packet dynamics from a monolayer-covered surface are reported. These dynamics reflect surface vibrational coherence in a monolayer of amphiphilic molecules deposited at the CaF2/air interface. The induced macroscopic polarization following coherent excitation of adsorbate CH3 vibrational modes displays quantum interference effects (quantum beats) and decays on a time scale dependent on the nature of the interfacial environment. These observations provide a link between the degree of interfacial order and the vibrational coherence lifetime and demonstrate that monitoring interfacial wave packet dynamics represents a new method for characterizing these important chemical regions.