I live in Budapest. There is a fabric store that sells quilting fabric on the main street (korut) that goes by the Nyugati Railroad station. This street changes its name at the intersection of the train station--to the east, it is called Terez Korut; and to the west it is called Szent Istvan Korut. When you walk out of the train station, you will want to get to the other side of the street and go to your right (towards the Danube River, which they call the Duna. I think the store in about one or two blocks from the train station. It is on a corner, and the door is set on a diagonal/kitty corner. There is a sign in the window on the street side of the store that says "Patchwork." I've been able to find quilting fabric there at, what is for Europe, very reasonable prices. There is another shop that is in the northern part of the city that is difficult to find, and I have not been there in a very long time. And another shop that I did not even know about is
Kerület Krisztinaváros Maros utca 29, 1122 called the fabrikashop.
Another thing to think about is this:
http://www.kekfestocotton.co.uk This is Hungarian traditional blue fabric. It is made in Szentendre, a small town just north of Budapest. You can sometimes find this fabric at fairs and street vendors; and they do sell packets of 4 1/4 meter pieces of fabric (I know--I just bought some). You can also buy it online here at the link above.
Have fun! You can connect with me privately if you wish more information. When will you be here? Carolyn