Try one of the nicer hotels near the conference centre. They usually have a hotel 'business centre' where you can fax for a fee, assuming they haven't stopped with faxes too.
Alternatively, scan and email?
If that's not what you need, try:
wirtualnyfaks.pl
or
tanifax.pl
or
e-fax.pl
Or Google 'popfax' for something similar in English.