I've been to Bistro Florian, 21 place Carnot (04 68 72 77 28) a couple of times. Place Carnot is the square where the markets are held on Tuesday, Thursday, Saturday (best day).
Very popular with the lunch time local crowds and perhaps a good idea to book. I've managed to get in there twice - and twice turned up at midday on the dot to find it full.
It's not a big place, not many tables. Food is reasonably priced and very good - and right at the edge of the beautiful square. about 10 years ago