Check with the company that insures your own personal vehicle to see if the coverage extends overseas. (This would be, most probably, only liability insurance).
Then check with your credit card issuer to see if you are covered for collission/personal property if you use the card for the rental.
I have never had to pay for additional insurance coverage (even when hiring cars in Europe) and I do not have any kind of special coverage with my personal vehicle.
Lately, some of the car hire companies have added a new "optional coverage" to their contract which takes into consideration the number of days that the car you will be driving might become inoperable should you be in an accident. Say, for example, you crash the car and it takes 1 week to repair. Some car hire companies are now asking to be reimbursed for the lost revenue for those 7 days, i.e. $25 x 7 = $175 or so. They offer you coverage to cover that which runs about $15 or so for the typical customer. So, you pay them $15 and they waive the $175 you owe them SHOULD YOU GET INTO AN ACCIDENT. That's a pretty bad deal if you think about it unless you are a very, very poor driver since that assumes a 1 in 12 chance that you are going to have an accident ($15 is about 1/12th of $175).
Bottom line: You probably don't need to pay for any additonal coverage. Check with the aforementioned and keep in mind that the car hire companies make a fortune by selling you coverage that you don't need and will most probably never use so don't let them intimidate you and read the contract carefully being careful to say "I want to decline all additonal insurance coverage (and that silly "lossed revenue" coverage as well".
Good luck!