Hi Steph,
The quality isn't great, but there are maps of Saigon at http://tinyurl.com/5qq67s. However, you don't need to know any district except District 1. A quick Google of "District 1 map Saigon" will give dozens of results, many with hotels marked. However, in my experience, many of the better deals do not take online bookings.
If you don't mind taking a 5-minute cab ride every morning to the conference, try Xuân Mai Hotel (xuan_mai_hotel@yahoo.com, 140 Cống Qùynh, +84 8 291 2860). It's at the western end of the backpacker district (Bùi Viện between Dề Thám and Cống Qùynh streets) and offers clean, comfortable AC rooms for $14/night. The owner even has another hotel nearby for $12/night I believe. There's also Sao Nam Hotel (haohlep@yahoo.com, 175/5 Phạm Ngũ Lão, +84 8 920 6472) which has rooms for $12. The rooms aren't quite as nice as Xuân Mai but it's a few blocks closer to touristy stuff. Really, there are dozens of good values if you are willing to go from hotel to hotel asking around. There are hotels around Bến Thành Market as well, and those would be walking-distance, although I have no experience with their prices.
The best bookstore I have seen is Fahasa at 185 Dồng Khởi and 40 Nguyễn Huế. There is also a small bookstore with a decent English selection in the Saigon Center, 65 Lê Lơi.
