My own site is necessarily personal and incomplete. Here are some that tend to be more extensive. Most of these are sites I consulted before I left, plus a few I've looked at since returning.
Americans going to Vietnam will need a visa from the Embassy in Washington, D. C.
These are only some of the sites which offer comprehensive information on Vietnam and Saigon.
These are surprisingly hard to find on-line, and even some you get locally aren't great. The best one I found was from a clerk in one of the bigger hotels (who may have thought I was a guest).
Vietnamese is not one of those languages even a multilingual Westerner can pick up quickly, but if you're feeling brave....