We went thru CAA for our rental with David's (which was a great way to stay!) I asked if it mattered what type of vacation it was and was told that since it was thru a CDN company that is registered with TICO we would be covered. I was worried because of the whole "timeshare" aspect and I'm not sure if we had rented privately if we would have been covered.
Just ask whichever company you chose to go with if David's would be covered.