My 2 stops at St. Lucia were via cruise ship, so can't help on housing. 2nd Time, dove, and with Scuba Steve's (in 2014 -
mini-trip report). SOFDiver had nice things to say about them, too (
thread). Blues Runner did
a 2016 Scuba St. Lucia and Anse Chastenet report. Mike C.'s
2015 thread, St. Lucia, included some input, including a link to a DAN Alert Diver magazine article on St. Lucia,
Estale.
Judging from the forum, St. Lucia doesn't seem to be a 'just a dedicated dive trip' mainstream destination, but you can have good diving while you're there. Our 1st stop was our honeymoon in 2006, and my wife & I did a tour including a rainforest hike that was neat. Practically no wildlife, but lushly vegetated. I recommend shoes that don't lend themselves to twisting your ankle!
I've thought about St. Lucia, but by the time I factored in housing (I'm a hotel guy; haven't made the jump to AirBnB, etc...), airfare & so forth for our little family, total trip cost was looking too rich for my blood.
Hope you'll post a trip report if you go!
Richard.