Caffe Mazzanti is one of the many eating establishments that line the Piazza dell'Erbe. They serve food and drinks from the early hours of the morning to late at night, but my favorite time to visit is for breakfast. Linger over a cappuccino or caffe con panna, and nibble on a cornetto (a.k.a croissant) or brioche. In nice weather you can sit out on the piazza under an umbrella and watch the world go by. A caffe macchiato will run you about twice (~$2.50) what one does in a less well-situated establishment, but the scenery makes it worthwhile.
Italian caffes take some getting used to by Americans. Food and drink cost more at the table (especially al fresco) than at the bar. Service may not be as efficient as in the States. But come and discover the joy of sitting out and watching the world go by long after you've consumed your one drink, without having the staff try to hustle you out to maximize table turnover!
Although the Piazza dell'Erbe is frequented by tour groups and has many attractions nearby, the Veronese still gather here. Come here in the afternoon for campari or a caffe correcto (espresso with alcohol, such as grappa) as well.