Actually, most deployments are now closer to 8 months, unless they're starting to get shorter again. Email is actually way more reliable unless something major is going on, but if you try to send mission critical info (e.g. we're pulling into this port on this day or coming home that day), expect to not have email for a while. You will have some internet, but as was stated earlier, it's a lot worse than dial up (which I'm assuming you're too young to remember), and until you're qualified, don't expect to use it very much if at all.
It will put a strain on your relationship.
Oh, and most of your division will assume you're going to try to get them to do all your work for you and that you'll get pregnant right before deployment, whether it's true or not is irrelevant, they're just going off past experience, so it's up to you to prove them wrong.