I believe Bulgaria, you are looking around February 2011 or so, just had a couple of friends book there and that is what they were given.
We booked about 1 month ago and we got in for October.
Have you considered Bulgaria, depending on your MS, i believe they are very good with PPMS.
The costs are about the same as Poland. My wife went to Poland in April, had some good results but are now long gone, we are going for a second treatment in Bulgaria, they tend to do the azygos more than Poland and this is what Dr Zamboni says affects PPMS the most.