As a rule, yes.
Pretty much every author I have heard speak on the subject says that to be a writer you should read as much as possible; in whatever genre or field you wish to write, so you'll know what is expected in it, and in other genres and fields to understand the relative hows and whys. Plus, because reading broadly almost invariably improves your educational background and thinking skills.
Now, for colloquial *speaking* a good resource is movie and TV DVDs.
Watch a movie repeatedly, with the appropriate language and subtitles, to fine tune your hearing to the nuances of the language in question. Of course, the source material should focus on a reasonable social setting... Medical dramas and police procedurals can be very useful, urban comedies... less so.
