Well, the weather system doesn't really apply to coffee that much. It is primarily altitude that affects it. It is also a permanent plant, so you don't have to spend time every year planting it and waiting for it to grow. It will just pop out with beans after a while. It is the most stable crop in the game really.
If you start adding canneries, you have to add a lot more infrastructure to maintain them. Add a cannery and a teamsters office, some more churches, doctors, apartments... As Canned coffee creates an income of 2400 pesos over the normal Coffee's 1300, it in general is not worth it. I usually make around 3k on the canneries producing coffee per year. During the course of the game, it is very hard to recoup those expenses.
It can be worth it however if you have an Airport and a TV station. You can get a 70% markup on coffee from either US or Russia through use of the trade delegation, and a 20% markup on processed goods through use of the industry ad campaign. Just to round it off... if you are entreprenureal (sp?) that adds an extra 10%, so your export price of canned coffee can be up to 4800 pesos, or 100% market value.
This is probably the only reason to build the canneries, as they do begin to make larger profits. You start off making 1100 pesos per load that goes through processing. With diplomacy you can get it to around a 2500 peso profit per load.. not to mention the base value almost doubles. Eventually it will pay for its own weight.
In the end, coffee can be a lucrative business choice. It can be similar to gold mining/jewelry manufacture in profit, but the collection of the material is fast, painless, and outputs for the most part the same every year (which is an enormous quantity). It's easier on the environment as well