Use 2 if you got em. Otherwise pitch one and you can add on later when you can get to the LHBS. But you know what? 1 pack will be just fine. There are many LHBS and online stores making a lot of money on yeast sales. So its in their best interest to scare you into buying "the correct amount" of yeast. Pitch rate calculators are good for determining the optimal amount of yeast, but we as homebrewers really don't need that kind of precision.
Funny thing about yeast is that it will multiply and eat as long as there is food present. Some argue that under-pitching can cause off flavors due to stressing the yeast, but in a 1.080OG beer, I am not sure you will notice those flavors anyway.
Coming soon: Myth busters - Homebrewing edition