According to the Exorcists the proliferation of the world with demons is tremendous. They know if you cheated on your taxes last year. The demons know for example what exorcist will be attending to whom even before he knows. When you are experiencing a really heavy temptation for example, it is a good bet they had a least something to do with it. This is why we are all assigned guardian angels, we have a very strong need for it. So yes, if someone is moving towards that direction, they will read, visit, and talk about such plans. It is a sure bet the demonic knows about it.
As usual though, they have to have permission to attack or to cause trouble. Free will of others can make our plans a little more difficult or helpful. God does not want us to worry about such things though. If God wants someone to work in their vineyard, and that person wants it as well, it will happen. If we take advantage of the sacraments, pray, and use sacramentals, there is often nothing to worry about.
