Also- I know when I weigh myself at home, I don't tend to have much on at all...and for some reason they frown on that at WW

If you had heavy winter clothes and shoes, it can make a big difference too. The best way to compare scales is to weigh yourself wearing the same clothes/shoes right before you leave or as soon as you get home- and try to not eat, drink, use the bathroom, etc between the two weigh ins. I've done that in the past to see how accurate my scales are compared to my doctors office- and they are pretty good. Its also helped me to realize its okay that if the doctors scales say I weigh 4#'s more then what I weighed this morning at home, because I probably do by that time in the day with all my clothes on.
Most digitial scales will give you the big ol' EEE if you're over their weight limit. You could try holding something that weighs 5 pounds or so, just to see if yours do. A gallon of milk or water weighs about 8 pounds- that should do it. I find my digital scales are pretty accurate, even when I'm in the 'danger zone' of close to 330- and mine were a cheap set I bought a few years ago when I did WW. I did the same thing- I joined for a short period of time, until I had all the basic info, then I did it on my own. One of my issues at the time was between my job and grad school (which were 150 miles appart- I lived in the middle), I couldn't go to the same meeting two week in a row so I never got to really know anyone feel like I belonged. And they all used different types of scales, so I questioned how acurate my weigh ins were. I think the whole Points program is a great system- I still use it to put a value on food to this day, though at this point I have to monitor more things so I am using FitDay.