You bring up a good point to which I'm still trying to understand. When I collected my first hive, someone mentioned that because the bees had built their hive underground they could be AHB. Being new to beekeeping became concerned about it and even questioned whether I wanted to take a chance with having them around my kids and pets. At first they didn't seem aggressive at all, I could hang out around the hive and open it to fill feeders without protection. As time goes on and their numbers have quadrupled, I'm getting a little more uneasy about opening the hive. However, as long as I use smoke, wear a veil and gloves, and move slowly there is no problem. As the hive grows will the bees become increasingly aggressive? Some beeks say re queening is absolutely necessary to ensure they do not become "africanized", which has become synonymous with "downright mean". Others seem to indicate it doesn't matter if they're africanized or not, bees are bees when it comes to managing hives, and being AHB may be a good thing to maintain healthy hives in our area as they are more suited to our climate. Thoughts?
First things first, in your area, I strongly recommend that you use full protection when working your hives. I do not say that lightly and I usually do not use any protection, especially gloves. I do recommend you do as I do and test your hives as I do with unfamiliar hives. I get close, wait for a responce, get closer and eventually pet the guard bees. Some bees will not let you get within 10' others do not let you pet them. I can pet all of my hives. I did have one hive that had at least one bee that would nail me at 10' once a week. I was always cautious with that hive. When they swarmed I used a bump bucket to put them in a box and when I bumped them off the limb I took about 10 stings to my head. I emptied them in a nuc but decided not to keep them and left the box open and they left. When that hive goes hot, it will be very difficult to re queen due to trying to find a queen with a full attack on. Read Michael Bushes The Practical Beekeeper to find out how to do it. Do a search and you can find it on line. I recommend you find a local beek and help him with his hives to learn the ropes.
African swarms often times are no more aggressive than European swarms and as you describe, start out pretty gentle until they have a hive worth protecting. They also grow in numbers very fast like you describe. Bee very careful. If you are going to bee a Beek where you live, check out the vented suites, Jacket and pants, from Mann Lake. They provide much better protection than standard suites.