It's actually more like 20 minutes if you have your own vehicle. It takes at least 5 minutes to get into Cruz Bay.

Westin St John is a terrific family resort as long as you remember itz in the islands mon...so expect island time, island service; so better to be limin' then gettin all upset

Went there this past October and here's a link to my trip report
http://tinyurl.com/y2s5vh