I dunno, I understand that you have a budget and all, but it's not always wiser to pinch pennies. I'm sure that you can make plastic grow bags work, but will your end product suffer? I'm more focused on giving my ladies the best most comfortable life possible before I chop them to pieces and hang them out to dry. Whatever you decide to do, just think of your plants first.
Now on to the plastic grow bags...lol. They look like they might fall over if you get any sorta decent wind, especially when your plants get taller. Also, if you set them directly on the ground, is your hardpack shit native soil goin to prevent the bags from draining properly? They say they have drainage holes poked into them, but probably on the bottom, and if those are flush to the hard ground you might have issues there. If you could take a hammer, maybe drive a 2 foot long piece of re-bar down through the bottom of each bag into the soil, that might prevent them from falling over when it gets windy. You might want to think about putting in some drainage holes on the sides about a half inch from the bottom. Obviously if you decide to buy them, try a few different experiments with them to figure out how they work for you.
You might be better off just buying bags of soil, setting them upright and propping them up between something. (i.e. more re-bar, wooden stakes, big rocks) Then you could just cut the top off the bags and plant directly in them. Just make sure you poke drainage holes in them first. I can imagine that getting pretty expensive fast, though, especially if you wanna grow like 50 plants. Soil ain't cheap unless you're buying it by the cubic yard...thats 27 cubic feet...Most bags in home depot and walmart average around 1.5-2 cubic feet a bag, though home depot has Kellogg All Natural soil in 3 cubic feet bags, compressed.
Anywho, these bags vary in price from 4.50-9 bucks a bag, and a cubic yard averages around 25 bucks, though you need a place to have it delivered, or sometimes you can pick it up if you have your own truck. Thats what I'm gonna do next season. Way cheaper to buy it by the yard if you can, and a lot of these soil companies will custom blend soils for you. You can ask them to screen it down to certain sizes, mix in perlite and other goodies, and it's all really affordable. Good Luck dude!