Great question Richard - I am wondering about the same thing. My AmEx has interntional car insurance and I am looking for about a month rental in March. If we individually find something out, let's post it here.
I'm glad to see this IL forum - right now it's a nice small group! 
Hi All - not a new member but i'm having trouble navigating the website...I would like to blame it on the website, but, well, you know how it is!!
I signed up for the Costa Rica bootcamp in July, but don't know where to go to find confirmation on the IL site. Can somone tell me where to look?? Thanks!! Ginger