Hi Danelle! I'm so happy that you are considering the great Mexican fare offered in Epcot! San Angel Inn and La Hacienda de San Angel are both amazing places to enjoy cuisine, with both offering great scenic backgrounds.
San Angel Inn is the original table service restaurant at the Mexico Pavilion in Epcot. It is located inside the Mexico Pavilion, right at the base of the Mayan ruins. Cuisine ranges from Tacos to Mahi Mahi. San Angel's coolest feature is the fact that the boats from The Three Caballeros attraction pass right in front of the restaurant!
La Hacienda de San Angel is the Mexico pavilion's newest dining addition. Pulling double duty as both a table service and quick service restaurant, La Hacienda has really come into its own. Originally know as La Cantina de San Angel, La Hacienda underwent a dramatic refurbishment in 2010, and opened to great reviews in 2011. Expanded to include indoor seating and table service allotments, La Hacienda offers authentic Mexican Fare at great prices! The best new addition are the windows that face World Showcase Lagoon; this is a great place to sit and enjoy some of their fabulous margaritas and watch Illuminations: Reflections of Earth.
Hope that this helps you plan your magical vacation!
-Malanie