I'm using Maraki MR12 AP's which operate only in the 2.4 spectrum. It worked fine for the most part, but definitely consumed a good portion of the available bandwith on the when running at 4CIF @ 15fps. Pay attention to proximity to the AP and other apps running on the WLAN
It uses both....one or the other...I use 2.4GHz as the camera only need 5-10 Megabits to work properly and its a 802.11g device...The HD version of these cameras will require 802.11n and use more megabits..
I've used them on both, now connecting with a Belkin N750DB at 5 gHz, but previously used a Trendnet TEW-432BRP and a Linksys WRT54GT, both at 2.4 gHz with no problems. One issue you might want to be aware of. The program to view these that comes with the camera is very difficult, if not impossible, to configure to operate on a 64 bit version of Internet Explorer, and will not provide all the functions under Firefox, so keep a copy of the old 32 bit version to run it. Haven't tried it with Chrome, but expect the same problems from an active-X add on. Blue Iris software is better, but you'll have to pay for it after the short trial period. There are apps for Blackberry and Andriod that work well to view, record, and control remotely. Just make sure you're getting the genuine Foscam camera, the cheap knock-offs aren't so good.