There are many hotels in Athens of different categories. The following Hotels are very close to the Conference Venue, just 4 to 5 minutes walk with reasonable prices:

Hotels (region) Telephone, Fax Email
President Hotel (Kifisias Str)  (+30) 210 6989000
Best Western EmBassy Hotel(Close to USA Embassy)  +30 21 0641 5000

Also Hotels located at Athes Down Town are suitable (Syntagma, Plaka, Monastiraki, Psiri, etc) since the Conference venus can be reached via Metro into 10 minutes at Most.