I'm not quite sure what time the Ubud market is open. Websites list different things, from opening at 5am or sunrise to closing at 9am or 6pm. Most seem to say that the locals shop in the morning and this is the best time to attend.
Breakfast was the agenda as well as curiosity that led us to walk through at the unholy time of 7:30am. There was a nice amount of activity without being crowded, with all types of fruits, vegetables, some meat and fish and even trinkets and flowers being sold. Luckily toward the end I found a couple of nice stalls with a lady combining a wet rice, vegetables, peanuts, beans and sauce. The persistent surrounding 4 or 5 people making orders was reassuring that this was a good place to order from.
The level below street also brought us to someone cutting up fresh jackfruit and a couple of chicken sate grillers (both of which were a little dry but tasted nice).
I also tried the local specialty of snakefruit. It looks like an acorn surrounded by snake skin and really tastes quite unappealing. I think bitter sweet is the closest I can describe.
Enjoy the sights, smells and foods.