I live here in Lancaster and love to eat out. Here are some suggestions:
For Mexican, go to El Serrano's; they have incredible Mexican and Peruvian Food.
The Log Cabin is the best fine dining restaurant in the county (great filet). Old Greenfield Inn is also very good, as are D&S Brasserie (try their tomato-cheese soup) and Symposium. The Stockyard Inn is going downhill; avoid it.
Yangs looks like a dive but has the best Chinese food in the county. Tony Wangs and Hong Kong Garden are the other 2 good Chinese restaurants. Avoid the King Buffet unless you have an iron stomach.
Portofinos has good Italian food, as does Fiorentinos.
Issacs has great sandwiches, slightly overpriced.
Shady Maple is the best smorgasbord. Millers is OK in the winter if you have a coupon. Dieners is good. Avoid Hershey Farms and Willow Valley.
Leola Family Restaurant is possibly the best for good PA Dutch food, especially turkey and filling. Stoltzfus Farm Restaurant is good also.
The best Bed and Breakfast in the county is Clearview Farms. They deserve their 4 stars.
There are plenty of other good places as well. Enjoy!