I've been using them for years....I think i've always used paypal like the other posters. Make sure you sign up for the email alerts and wait until you get any alert for 80% off code (which happens once a month) most of the coupons never expire so if you don't use them on this trip you can always use them next trip.
Also if I have to give an address as a "U.S. address" I type everything on the line #2 (street address) and then choose CA as state, & 90210 for zip code
EX:
Mamudduck
123 Any Street
Peterbo,Ontario, Canada K9K 1K1,
CA, 90210
never had a problem.