Hi Linda! There are 2 rivers that circle the city center. I would recommend staying within that circle, because it will make walking to each market much easier. Also last year, entry points into the city center were subject to search for safety reasons. If you stay outside the circle, there is a chance your belongings will be searched each time you enter, which could be a little bit of a hassle. It looks like the Best Western falls just outside of that zone. There are lots of reasonably priced AirBnbs in that area, which is the route I took. Here is a map of the Christmas Market layout from 2018, and it gives a good overview of the area I recommend staying: https://noel.strasbourg.eu/documents/1356039/1389026/plan-marches-noel-2018.jpg/e0b1b85d-b709-31c9-563d-23c913265b38?t=1540917225842
I am sure this year’s layout will be nearly identical. I hope you have a wonderful trip! Let me know if you have anymore questions:)