Hm, not sure about the 2 liter bottles, but you can definitely use 3 liter soda bottles. I went to the grocery store and bought 6 of them for around $7, dumped out the soda, and that's what I use instead of a 6 liter bottle.
I usually put all the beer in the bottling bucket as usual with the same amount of sugar water (for me that's 1 cup of sugar dissolved in water), then rack the beer to the 3 liter bottles and whats left goes in a 5 gallon keg. While the 3 liter bottles are naturally fermenting, I take one right away and put it in the fridge to cool down, then add one CO2 cartridge and let that sit overnight, then when I wake up in the morning I add the second CO2 cartridge. You get force carbonation in a day or two, but it gets better as it sits.
Hopefully as you've enjoyed the first or second 3 liter bottle, the others have finished naturally carbonating and can be enjoyed right away...
DT