The salt is effective if dosed at the levels explained above. Lesser dosages won't do the trick.
Temperatures higher than 86F are also effective...unless you have one of those new heat-resistant strains. Temperatures lower than 86F will still speed up the life cycle of Ich, but won't kill it.
I agree wholeheartedly with
neutrino
above; you must consider the types of fish you have before choosing a course of action. Things like temperature sensitiviy and required dissolved oxygen levels vary from species to species. If you have live plants, that's another concern, as is the presence of snails, shrimp and other invertebrates.
I have no access in Canada to fish medications, but I used just salt and/or heat even before that particular legislative boot came down on my neck. Salt will remain effective until you remove it be means of water changes, so it has much the same benefit as a copper treatment.
For sure, you will need to do something that will continue its effectiveness while you are gone, without relying upon someone else to re-dose or otherwise mess with your tank. Ich isn't the End Of Days for your fish; treated intelligently, it's very easy to control and eradicate. Good luck!