Kipp, it's not quite that easy. First off if you are a Canadian company you must translate your US dollar revenues into Canadian dollars, with a higher Canadian dollar those revenues are increasingly less all other things being the same. That means your earnings will be less. If Canadian investors rather than US investors set the market (which is largely the case) then their will be negative pressure on the share price all other things being the same. This of course isn't effected by where your mining operations are located.
Now the decline in the peso will lower ones' operating costs in Canadian dollars but Mexican originated costs are generally a very small proportion of total costs and operating costs are usually a very small percentage of revenues, so the benefit should not be over stated.
As for debt, if the debt is Canadian debt then it is immaterial, but if the debt were in US dollars, then of course it would take fewer Canadian dollars to pay the interest or principal on that debt and that would be a benefit for sure. Again many of these companies could not raise a lot of debt and had to use equity to finance their startups.
Other than the above I would generally agree with your observations. Actually it sort of a win-win situation, in a rising Canadian dollar environment, you win by investing in Canadian companies through the exchange rate, I win even if I don't invest because my Canadian wealth (houses etc) are increasingly worth more US dollars (cheaper vacations, cheaper imports (food for example)); even our gasoline prices have become relatively cheaper etc).
AI
