Always DIY - cheaper and so much more satisfying than following the lollipop......lots of sites out there will help you. Try google and cruise ports call boards - the first result.
Hi, we too are on this cruise, i read up about these places and found that a organised excursion is needed at ho chi min city as its 2 and half hours from the city, hope that is of some help. CAN T WAIT FOR THE HOLIDAY! COUNTING DOWN THE DAYS.
No there is no need to do the ship's tour in HCM - if you go to the site referred to you will find many recommended private guides listed.
You can get to HCM on your own by catching the hyrofoil which will cost $12 US one way and take 1 hour compared to the road which does take 2 hours minimum.