I always eat at La Fonda when I'm in San Antonio. The atmosphere is very casual, with brightly colored walls, painted wooden booths, and fun decor. The crowd is mostly locals and some families.
The food is Tex-Mex, which offers tons of different combination plates and specials. Chips and salsa are free. The salsa is homemade and usually hot enough. The meal also comes with fresh, warm tortillas. I eat them with butter and salt.
I always start with a guacamole salad. It is shredded lettuce and a slice of tomato topped with fresh guacamole and a bit of hot sauce.
I would also recommend the queso. It is either served in a separate bowl or as a side right on the plate with the rest of the meal. It is good with chips and tortillas or mixed in with some rice and beans.
I hear that the margaritas are excellent, although I've never tried them.
The prices are very reasonable. Check out their website for the full menu at http://www.lafondaalamoheights.com/index.html
Dessert options are pretty minimal. Sometimes I get the sherbet, but last time they only had orange.
You pay your check up front at the cash register. In a basket on the counter are pralines for $1 each. Be sure to pick up several. Since they are fresh, they tend to dry out in a few days, so you may want to keep them in a bag.
If you have time before dinner, there are some cute shops in the Sunset Ridge Shopping Center where La Fonda is located.