Yes, you'll find good vendors everywhere. Just stick to the good vendors, wherever they might be. Look for the busiest ones that are being mobbed by locals.

Also, I generally avoid the downtime between mealtime rushes, as it tends to be leftover food that's been sitting too long.

ds37 said what I was going to say -- there really aren't any foods that are exclusively for mornings. Breakfast is simply a meal that's eaten after sleeping and before lunchtime.

Eat whatever looks fresh and delicious from whichever stands have lots of traffic and fast product turnover. Don't spend too much time "window shopping" as the best vendors often sell out.