darpin,
just water the heck out them before you go. forget about them for a week and enjoy your vacation. the idea of the vacation is to take a break from ALL of your worries. if ti eases your mind, remember, it is a weed. and it thrives in deserts (among other areas). the 6-7 days without water might actually strengthen the plants. i do this every year -- water them well, keep them on 24/0, take off for 7 days (enjoy myself) and i've yet to lose a plant.
hope this helps and enjoy your vacation.
booch