I'm sure I'll notice more things eventually, but here the ones that come up most often:
The plumbing here sucks. Consequently, all toilet paper gets put in a trash can, never flushed. This actually didn't take too much getting used to, but sometimes the toilet won't flush all the way, which is rather annoying.
Water is scarce here, so we try to conserve as much as possible (this may explain the first note some). You pay for all the water you use (as in, every house has a tank under it, and when that tank is empty, you have to buy more water). There are a couple gorgeous fountains around here, and I noticed that they get turned off at night; once I realized that, I realized how extravagant it must be to build fountains in a place where water is such a valuable resource.
Guys whistle at girls here. I doubt this fact will surprise anyone. Personally, I haven't had any unpleasant experiences with this; mostly just honks from passing cars and and a rather cool experience yesterday on the way to school when a guy whistling a song smoothly slipped in the cliche hot girl whistle. A couple of my classmates have had slightly more invasive experiences, but nothing unfortunate. Apparently it's actually common for the subjects of the catcalls to say thank you.
As I mentioned in my first post, the traffic here really is nutso. I feel proud of myself everytime I get to other side of a street alive (which has been every time so far!). What the result of this really is, is that sometimes we attempt to use crosswalks but more often than not our routes are very opportunistic. Even if it's a red light, if there are no cars you GO FOR IT because who knows when you'll get another chance?
There are many stray dogs, and they all look quite healthy.
Lunch, or La Comida, is eaten quite late in the day; for most of group, between 3 and 4:30. It is the largest meal of the day, when the family comes together to socialize. Dinner is often skipped altogether.
As I said, I'll probably come up with more things later on, but there's a taste for you.