Any advice for a traveller in South Vietnam?

Then I think Vung Tau is perfect place for you. Vung Tau is far from HCMC about 120km and it takes nearly 3hours to come there by bus. You should take buses which are well-known with high quality. Mai Linh, Kumho Samco, Hoa Mai should be the names to consider. Maybe, ask your hotel for booking ticket. You can also get Vung Tau by ship from HCMC. It takes shorter time. I haven't tried this way but I think it's more interesting.

Nice trip!

Phu Quoc island, Con dao island, Nhatrang beach...I was in there and they're pretty cool. From Hochimin I reached these 2 islands by plane; from HCM to Nhatrang by coach... very excited! Vung tau is kinda good, just like a small Miami.

Talking about Vietnam war is NOT weird. I was in a museum in Hochimin city near the Reunification Palace (don't remember the name but it's totally about Vietnam War and its evidences.). They told me all about Vietnam war and it gave me an inpressive that they could talk about this painful war with a smile in their face.

As you're a self confessed beginner, take the excursion. you're much less probable to wander away or ripped off (even if the spivs will aim you as you will supply off that candy scent of a shuttle virgin and that they could have the means to discover you a mile off).

i'd get out of Saigon as quickly as you can unless you're going on a shopping spree.

for a one week holiday in the south I'd take the bus to Nha Trang and enjoy the beach...

Don't mention the vietnam war.