AVCHD uses bitrates of up to 15Mbit/s or 17Mbit/s where Class 2 SD/SDHC cards should be OK, unless the cards stick too close to the required minimum of 2MB/s.
"This means that there will be, for example , 2GB SD 2.00 Class 2``SD Cards""and 4GB SD 2.00 Class 2``SDHC Cards""."