The ferries run back and forth every hour on the hour until midnight from St Thomas. You can hang at Duffy's in Red Hook, a popular hang out spot. In Cruz Bay there are several starting with Woody's.

RL

The very positive thing about both islands is that there are several "hot spots" in the same general area. Go to Red Hook and start at Duffy's - if you're not happy - head across the street to Molly Malones or Caribbean Steakhouse. Same in STJ - as Ron said - start at Woody's then you've got Quiet Mon next door and Morgan's Mango and others within a couple blocks.

Good Luck! Have Fun! (and be safe!)

Also suggest Island Time Pub (the old Sopchoppy's) in Red Hook near the American Yacht Harbor (2nd floor). Great view of harbor, awesome pizza, cheap beer. Good for any night of the week. Also in STT, the Green House in C.A. has happy hours daily from (I think) 4 to 7 pm with 2-for-1 drinks. Duffy's in Red Hook is a good "later on" place, like after 9 pm.

In St. John, I'd add the Beach Bar. Sunday nights are pretty hoppin' with the jazz bands.

Here is a video made by Travelistic.com regarding night life in St John...
ENOY!
http://www.youtube.com/watch?v=2xXPftyfDa0
But in my opinion...Just being there is enough! You will find entertainment if that is what you desire!
Amy