Drop Zones are very friendly places full of free-spirited folks. It really is a culture of its own, which can be intimidating at first. Just go on in and introduce yourself. Pacific Skydivers is a good drop zone. Tell them you're mildly interested in skydiving (even if you're not) and ask them if you can hang out and take some pictures. Here's some generalized guidelines to follow:
1) Most drop zones have a line that separates the general public from the landing skydivers. In skydiving parlance, it's called the beer line. They don't want Joe Public getting nailed by a landing jumper, so a line in the sand helps maintain order for everyone. It's called a beer line because if a skydiver lands on the wrong side of it, they have to buy beer for everyone. (skydivers have been known to drink a lot of beer after the last jump of the day) Ask them where the beer line is and make sure you stay on the right side of it!
2) Hang out long enough and once they get to know you, they may eventually let you into the landing area to take pictures. If/once you do, the best thing to do is pick your spot and not move when jumpers are coming into land. This keeps things predictable for the jumpers. If there are really experienced jumpers performing high speed landings, they may whiz by you at great speeds (50 mph) making for great photo opportunities.
3) If you really want to make friends, donate some pictures to the drop zone and some of its staff members. Selling a picture to an experienced regular jumper is ok. But whatever you do, do not try and sell pictures to students (or give them away). Every drop zone has videographers that sell video and stills...and this is their livelihood.
4) Hang out long enough, and you'll see some crazy stuff. Skydivers are a fun bunch!