It certainly depends on what you are looking to find. It also depends on whether or not you have some knowledge of the subject you are researching. There is much extremely valuable and accurate information on the Internet.
It is always wise to be cautious.
If you want technical advice, there is a wealth of information available. Since this information is based on mathematics, a lot of it is excellent. But, certainly not all of it is useful.
If you are looking for the facts behind a story, good luck. The information available here is worth about as much as you will find in any newspaper. It depends on the slant of the writer and/or news organization that presents it. It is said, Believe half of what you see and none of what you hear. That applies here (but maybe we should adjust the percentages, eh?)
My language skills arent perfect, BUT. I always, either consciously or unconsciously, judge information I read in the light of the grammatical skills of the writer. And I do this in the context of the topic at hand. On this board, you get a feeling for the reliability of certain posters and of the sensationalism of others. I think this would be generally true of most boards. Grammar is not at the top of the list here because of the confidence I might have in the information a certain poster consistently presents.
But, if I enter a site that claims to represent a viewpoint on a topic, and I see that the writer uses poor English (or Spanish), I might read it but I will discount up to 99% of what I read. And this depends on the subject as well as whether or not I know OF the writer.
You want to study a language? The Internet is a great source. You want accurate information about the Watchtower Society, the Mormons, or any other religious group? You takes your chances.
The Internet is only a source of information and links to more information. There are no guarantees of accuracy.