Sounds like a tough assignment! I teach adults, and have tried using Mark's hand-outs, which are great for beginners, a library of useful words. I know adults might not need the pictures, but it certainly makes learning more entertaining. I don't know if Mark has a set of flashcards intended for office use. If not, you could make your own hand-outs if you use the tools available in http://www.eslhq.com/gallery/
I think Mark's flashcards are much better, (his are the best) but of course it is against the rules to change them.
Secondly, you could try teaching simple phrases. If the phrases translate easily into their mother tongue, they will learn faster. For example, in Austria, I can teach them the word for desk (Tisch), or I can also teach them the phrase "here is my desk" because it is so similar to German that the students latch on quickly. Because your time is so limited, I think Mark is right about using direct translations and worksheets. Kids soak up new words more easily, whereas adults will constantly want to know: how do you translate this and that.
I've also used the dialogues in Bogglesworld. They cover the topic well, and they add variety to each situation. But you might find them a bit too advanced if your students are raw beginners. If you have the time, you could go over the phrases which you believe your students will need most, and then revise the dialogues, tune them down a notch, to simplify the conversations. Give them dialogues to try out. Most adults I've worked with enjoy pair work; they like to get a chance to practise. Change the partners often.
You can get your students to move around a bit by setting up different stations in the classroom with different, or related, dialogues. If, for example, you are teaching phone dialogues, a few stations could be:
1) the number is busy (that one is so easy that they love it)
2) the person you need is not there, so you leave a message
3) the person you need is not there, but you don't want to leave a message
4) you reach the wrong number
5) you finally get through and hold a short conversation.
You can always spice up the dialogues by adding something unusual which makes your students laugh. For example, if someone phones and wants to talk to (a person), you can answer that the person is in the bathtub. Again! It sounds silly, but if the person happens to be one of the participants, they all begin laughing. I like to use the participants' names. It makes it more personal. And I throw in something kind of weird, but easy to understand. They catch on fast, and they enjoy the material.
Good luck and have loads of fun!