I'm asked this question a lot. I run errands in that area but other than GiNa's, I never eat around there.
GiNa's a great place for lunch, especially if you're craving a salad. They have a fantastic selection.
The decor is hip and bright and it's excellent people watching. The crowd is a mix of chic Roman mommies and fab singles with Birkins, Chanel's 2.55, etc., business lunches, high school students from the private school nearby, and the occasional tourist. Prices are moderate, especially for the area. Reservations are recommended. It can get packed, especially during nice weather and sales season.
My friend Shelley wrote about GiNa a few years ago HERE. At that time she raved about their picnic lunches. I don't know they still do that. I've only been to GiNa during the fall/winter.
The New York Times also wrote about their picnic lunches.
Via San Sebastianello, 7/A
Piazza di Spagna
If you have a favorite place for lunch (and/or dinner) near the Spanish Steps, please feel free to share in the comments.