Time-dependent studies of the excited state dynamics of betaine-30 in acetonitrile at room temperature have been carried out using a mixed classical/quantum molecular dynamics simulation methodology. The Jr-electron system of the solute molecule is treated quantum mechanically using the semiempirical Pariser-Parr-Pople Hamiltonian, including the solvent influence on electronic structure. The remaining interactions are treated via empirical potentials. Transition probabilities between adiabatic electronic states are evaluated using surface hopping methods, including all nuclear degrees of freedom in the coupling. The dynamics treats the (rigid) solvent and the dihedral angles for relative rotation of rings of an otherwise rigid solute classically. The contribution of all remaining solute intramolecular vibrations is included in the nonadiabatic coupling via an approximate, but purely quantum mechanical, treatment. Analysis of the dynamics reveals that, after excitation to the first excited state, the energy gap between ground and first excited states of the molecule exhibits an ultrafast (similar to 100 fs) decrease due to the inertial response of the solvent that accounts for about 70% of the solvent response, followed immediately by a further subpicosecond solvent component. The times and amplitudes of these solvation components are in accord with the results inferred from resonance Raman spectra, and the solvent contribution to the Stokes shift observed is in accord with values inferred from ground state absorption spectral line shape analysis. However, we also find that the energy gap exhibits a slower picosecond time scale response of comparable magnitude due to relative rotation of the central phenolate and pyridinium rings. This relaxation has not been previously noted or incorporated in corresponding electron transfer models. Analysis of contributions to the electronic nonadiabatic coupling shows that this is dominated by a small set of high-frequency intramolecular modes of the betaine-30 molecule, with the solvent making a relatively very small contribution, also in agreement with previous experimental inference.