Contradicting most rules about dining in major tourist centers, restaurants on Santa Fe Plaza [1] and right around it can be quite good—and if the fajita cart is set up, definitely stop there for lunch. The blocks within the ring formed by Alameda Street and Paseo de Peralta contain some classic Santa Fe [2] spots to which everyone makes a trek at some point, along with a few hidden treats.
Links:
[1] http://www.moon.com/destinations/santa-fe-taos-albuquerque/santa-fe/sights/downtown/santa-fe-plaza
[2] http://www.moon.com/destinations/santa-fe-taos-albuquerque/santa-fe