Hello Erika and Nina,
Though I'm not living in Tokyo, I've asked around about hotels, and have received a couple of recommendations (below). Mary Hillis may have additional suggestions:

Kumamoto Kaikan
http://www.greenhotel.co.jp/hotel_list/kumamotokaikan/index.html (no
English site yet)
6-5-19 Roppongi, Minato-ku, Tokyo, 112-0004 JP
Tel. 03-3402-8377
Fax 03-3402-8373

Ochanomizu Inn
http://www.greenhotel.co.jp/hotel_list/ochanomizu/index.html (English, top right)
2-6, Kanda-Awajicho, Chiyoda-ku, Tokyo, 101-0063
Tel. 03-3255-4161
Fax 03-3255-4962
Both cost a little under ¥10,000 = $ 101 a night for single rooms, including breakfast. That is towards the low end of modest accommodations in the metropolis. For both, check-in is at 15:00, and check-out, at 10:00.
The Kaikan, a small hotel a couple minutes from Roppongi night life, apparently has wireless access in the lobby:
http://ipass.jiwire.com/wi-fi-wireless-hotspot-Tokyo-Tokyo-JP-Kumamoto-Kaikan-1F-lobby-1194002.htm The Inn, which is a bit larger and close to the electronics shopping district, Akihabara, offers modems for

internet connections in guest rooms.
Both are in very convenient locations, near subway or surface rail stations. In Tokyo, not using the Metro really isn't an option!
Cheers, Paul
________________________________________________________________________________
HI Nina,
The place below looks good and is cheap since it has dormitory style accommodations. The four of you might be able to share a single room.
http://www.sakura-hotel.co.jp/sakura-hotel_rates.html#dormitory The dormitory style is only 3780yen a night which is less than 40 USD.
Of course, there is also the cost of food but you can eat fairly well for less than 2000yen a day, particularly if you buy food at convenience stores which are everywhere.

It seems that this company has three hotels. Here is another one.
http://www.sakura-hotel-ikebukuro.com/Hope this helps.
--Tom