The ASCJ does not designate specific hotels as conference hotels, and has not made special arrangements for conference rates. The following are just suggestions for specific train stations that are both convenient to the conference and have a variety of hotels at reasonable rates.
Hotels around Urawa Station, specifically The Met and the Washington Hotel, are most convenient and fairly reasonable by Japanese standards. Getting to the conference would require taking the train one stop to Kita Urawa (no hotel options here) and then riding to Saitama University. Also try Saitama Shintoshin, 2 stops from Kita Urawa. Hotels in either Akabane or Omiya, both within 17 minutes* from Kita Urawa, are also conveniently located. Further out, but still convenient and more variety, are hotels in Ueno (27 minutes [Tokyo-Ueno Line]), Ikebukuro (25 minutes), Shinjuku (34 minutes), and Tokyo Station (35 minutes [Tokyo-Ueno Line]) areas. Akabane, Omiya, Tokyo (46 minutes but no transfers) are on the Keihin Tohoku Line which connects directly with Kita Urawa; Ueno and Ikebukuro have trains to Urawa, which require a very easy transfer to get to Kita Urawa. The Saikyo Line from Shinjuku, Ikebukuro, Akabane connects directly with Minami Yono. See the Location/Access option under the Conference option for more detailed information on transportation.
The Tokyu Stay Hotel is a nice chain, with hotels close to train stations, reasonably priced, and individual laundry facilities in the rooms.
*Train times between stations vary depending on the train. Many of the stations listed here offer multiple ways of reaching Kita Urawa station.
You can also find hotels in Saitama via internet discount hotel guides such as: