Yangzhou (Huaiyang) cuisine represents Zhenjiang, Huainan, and other places found along both side of the Yangtze River. However, Yangzhou itself is a small city which is best known for its "Baozi."
Baozi is a type of steamed bun, which can be stuffed with sweets and meat. Baozi sometimes can be served as a breakfast meal, and it is best to eat it while it is hot.
Huaiyang cuisine is known for being light and sweet tasting. If you are a tourist and do not like spicy (Sichuan) and strong foods, then Huaiyang is perfect for your taste.
Myself, I do not know a lot of Huaiyang dishes, however the two dishes you should try are Yangzhou fried rice and Beggar's Chicken.
Beggar's Chicken is chicken marinated with spices and wrapped in aluminum foil. And no, this is not food for homeless people. Traditionally, Beggar's Chicken will be wrapped in leaves or sometimes even in mud. Cooking the chicken this way will help you to capture the full taste of the chicken.
This is very hard to describe. You may need to try it, and then describe it in your own words.
Because Yangzhou is close Nanjing, you will be able to enjoy the mix of northern and southern cuisines. When stepping foot into Nanjing, the dish that you should try is duck blood. Meaning blood that has been congealed into a solid form and mixed with noodle soup.
If you are into diet and healthy food, then tofu is the name of the game. Nanjing is best known for their stinky tofu, and to me it is very stink. I recommend that you just try it once because of the hot sauce that comes with it.