I'd say hit Rosarito for the afternoon but not stay there. Head South to either (Los Rocas, Baja Beach Resort or La Fonda). Each are a quick ride from Rosarito and near Puerto Nuevo.
Lobsters are small right now in PN but go for the experience anyway. Just walk the street and let them argue prices. Just back and Ortegas was the cheapest and biggest which has NEVER been hte case. It's the nicest resturaunt in town.
La Bufadora is nice (a little overbuilt over the years but fun)
Wine country on HWY 3 is nice as well.